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PubMed1994

The duration of prolactin secretory bursts from the pituitary is independent from both prolactin and gonadal steroid plasma levels in women and in men.

The intrinsic secretory characteristics of prolactin (PRL) have been investigated using newly developed algorhythms for instantaneous secretory rate (ISR) computation. PRL secretory rate, its intrinsic pulsatile characteristics and their possible dependance from gonadal steroids were investigated in five groups of subjects: a) 11 women during the follicular and luteal phase of the same menstrual cycle; b) 5 healthy postmenopausal women; c) 6 women affected by functional hyperprolactinemia; d) 5 normal men; e) 4 agonadal subjects before and during testosterone replacement therapy. All subjects underwent a 6 hours pulsatility study, from 08:00 to 14:00, sampling every 10 minutes. PRL plasma concentrations were determined using a RIA system and the presence of PRL secretory pulses was evaluated with program DETECT, both on plasma time series and after ISR computation. A distinct PRL episodic release was observed in all groups (follicular phase: 5.5 +/- 0.5, luteal phase: 6.5 +/- 0.6, postmenopause: 5 +/- 1, hyperprolactinemic women: 4.2 +/- 0.8, men: 4.8 +/- 0.4, agonadal before testosterone: 6 +/- 1, agonadal during testosterone administration: 5.3 +/- 0.3 peaks/6h), but mainly the computation of ISR allowed to demonstrate that the duration of the lactotropes secretory events was constant in all groups studied. PRL secretory bursts duration ranged between 23.1 +/- 1.8 and 25.4 +/- 2.5 minutes independently both on PRL or on sex steroid plasma levels. In conclusion, the present report shows that in different physiological conditions the intrinsic secretory bursts from lactotropes are constant in duration independently from the functional state, sex and the steroid hormone levels.

Adult↗
PubMed1990

Secretory patterns of 1 alpha-hydroxycorticosterone in the isolated perifused interrenal gland of the dogfish, Scyliorhinus canicula.

An isolated in-vitro perifused interrenal gland preparation from the dogfish Scyliorhinus canicula was used to study production of quantitatively the major corticosteroid 1 alpha-hydroxycorticosterone (1 alpha-OH-B), measured by radioimmunoassay. Basal secretory rates were 877.1 +/- 145 (S.E.M.) fmol/mg per 15 min (n = 14) and the preparation remained viable for up to 22 h, as reflected in a brisk response to 10 microM cyclic AMP (cAMP) after this time. Steroid production responded in a dose-dependent manner to porcine ACTH, with 10 microM producing a maximum stimulation of 225% above the basal secretory rate. cAMP (10 microM) produced an increase of 278% above basal, while 1 microM forskolin increased basal secretory rates by 127%. [Val5]- and [Ile5]-angiotensin II (0.1 microM) increased 1 alpha-OH-B production by 120 and 372% respectively over basal secretory rates. Increasing the concentration of K+ in the perfusate from 8 mM to 12, 18, 28 and 40 mM produced a significant rise only at 28 mM. Alterations in the concentration of Na+ and osmolarity of the perifusion medium had inconsistent effects on steroid production. Increased concentrations of urea (from 360 to 720 mM) increased the basal secretory rate by 121%, whilst reducing the concentration of urea (from 360 to 90 mM) had no effect.

Adrenocorticotropic Hormone↗
PubMed2003

Examining synaptotagmin 1 function in dense core vesicle exocytosis under direct control of Ca2+.

We tested the long-standing hypothesis that synaptotagmin 1 is the Ca2+ sensor for fast neurosecretion by analyzing the intracellular Ca2+ dependence of large dense-core vesicle exocytosis in a mouse strain carrying a mutated synaptotagmin C2A domain. The mutation (R233Q) causes a twofold increase in the KD of Ca2+-dependent phospholipid binding to the double C2A-C2B domain of synaptotagmin. Using photolysis of caged calcium and capacitance measurements we found that secretion from mutant cells had lower secretory rates, longer secretory delays, and a higher intracellular Ca2+-threshold for secretion due to a twofold increase in the apparent KD of the Ca2+ sensor for fast exocytosis. Single amperometric fusion events were unchanged. We conclude that Ca2+-dependent phospholipid binding to synaptotagmin 1 mirrors the intracellular Ca2+ dependence of exocytosis.

Animals↗
PubMed1995

Enhanced biliary excretion of canalicular membrane enzymes in estrogen-induced and obstructive cholestasis, and effects of different bile acids in the isolated perfused rat liver.

BACKGROUNDS/AIMS: Canalicular membrane enzymes are normally released into bile by partially known processes. This study was undertaken to investigate whether hepatocellular cholestatis induced in rats by ethynylestradiol or obstructive cholestasis produced by complete biliary obstruction for 24 h is associated with an increased release of alkaline phosphatase and gamma-glutamyl transpeptidase into bile, and to clarify how this process is affected by different bile acids. METHODS: The studies were performed in the isolated perfused liver during infusion of sodium taurocholate, taurochenodeoxycholate and tauroursodeoxycholate at increasing rates. RESULTS: Maximum sodium taurocholate, taurochenodeoxycholate and tauroursodeoxycholate secretory rates were decreased in both cholestatic groups (complete biliary obstruction > ethynylestradiol) compared with controls. Maximum biliary outputs of alkaline phosphatase and gamma-glutamyl transpeptidase were significantly increased in the ethynylestradiol group during infusion of sodium taurocholate and taurochenodeoxycholate, but not of tauroursodeoxycholate, and were increased in the complete biliary obstruction group during the infusion of sodium taurocholate and tauroursodeoxycholate but not of taurochenodeoxycholate. The biliary outputs of alkaline phosphatase and gamma-glutamyl transpeptidase showed a significant and direct linear relationship with sodium taurocholate and taurochenodeoxycholate secretory rates in both cholestatic groups. However, only in the complete biliary obstruction group did alkaline phosphatase and gamma-glutamyl transpeptidase excretion show a significant correlation with tauroursodeoxycholate secretory rates. The slope of the line, which indicated the mU of enzyme activity secreted per nmol of sodium taurocholate or taurochenodeoxycholate, was greater for gamma-glutamyl transpeptidase and alkaline phosphatase in both cholestatic groups (ethynylestradiol > complete biliary obstruction) than in the control group. Alkaline phosphatase activity in purified isolated canalicular and sinusoidal membranes was significantly increased in both cholestatic groups (complete biliary obstruction > ethynylestradiol), while gamma-glutamyl transpeptidase activity was unchanged compared with controls. CONCLUSION: The marked increase in sodium taurocholate and taurochenodeoxycholate-mediated release of alkaline phosphatase and gamma-glutamyl transpeptidase into bile in cholestatic rats suggests an increased lability of these intrinsic membrane proteins to the detergent effects of secreted bile acids. It remains to be elucidated whether this phenomenon, which was particularly intense in ethynylestradiol induced cholestasis, is important in the pathogenesis and perpetuation of bile secretory failure. In contrast, tauroursodeoxycholate administration did not result in enhanced biliary excretion of these membrane enzymes, in either the control group or the ethynylestradiol group, supporting the concept that this bile salt lacks the membrane toxicity of common bile acids.

Alkaline Phosphatase↗
PubMed1984

The self-priming effect of gonadotropin-releasing hormone on luteinizing hormone release: observations using rat anterior pituitary fragments and dispersed cells continuously perifused in parallel.

To study in vitro the self-priming effect of GnRH on LH release, rat anterior pituitaries were prepared either as fragments or dispersed cells and continuously perifused in parallel chambers. The experimental groups consisted of rats killed at 0800 h on diestrus day 1, diestrus day 2, proestrus or estrus, or at 1400 h on proestrus. To insure truly independent observations, each experimental preparation was tested on three occasions. After basal LH release had stabilized, the tissue preparations were exposed to 10 nM GnRH as two 30-min challenges separated by 1 h. LH secretory rates (nanograms per min/pituitary for fragments; nanograms per min/10(7) cells for dispersed cells) were calculated 1) for basal release (during the 20-min period immediately preceding each GnRH challenge), 2) in response to GnRH, and 3) as the sum of basal and GnRH-stimulated release. Comparison of the two preparations revealed that basal and GnRH-stimulated LH release by pituitary fragments was more variable than LH release by dispersed cells. In addition, while dispersed cells responded promptly to the addition/withdrawal of stimuli, fragments did so more gradually. With respect to GnRH self-priming, the second mean secretory rate for basal LH release by fragments (range, 28.8-46.5) was significantly (0.1 greater than P greater than 0.01) higher than the first rate (range, 14.4-22.0) on diestrus day 1, diestrus day 2, proestrus at 0800 h, and estrus. With dispersed cells, the first and second basal rates were similar to each other on diestrus day 1 and estrus, but on diestrus day 2 and on proestrus at 0800 and 1400 h, the second basal rate (range, 36.8-93) was significantly (P less than 0.001) higher than the first range (range, 17.7-31.7). When fragments received GnRH, the second mean secretory rate (range, 35.2-64.2) was significantly (0.1 greater than P greater than 0.03) higher than the first rate (range, 13.4-34.1) on diestrus day 2 and proestrus at 0800 h. With dispersed cells, the mean secretory rate in response to the second GnRH challenge was higher only on diestrus day 2 (37.0 +/- 4.1 vs. 60.3 +/- 3.8; P less than 0.05). When considered as the total of basal plus GnRH-stimulated LH release, the second secretory rate by fragments (range, 54.5 - 110.8) was significantly (0.1 greater than P greater than 0.02) higher than the first rate (range, 27.9 - 51.4) on diestrus day 1, diestrus day 2, and proestrus at 0800 h.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

[Different effects of taurocholate and ursodeoxycholate on the maximal rate of biliary sulfobromophthalein secretion in hamsters].

Because of the special physiochemical properties of ursodeoxycholate and its tauroconjugate, the effect of these two bile acids on the maximal biliary secretory rate of sulfobromophtalein was compared to that of taurocholate in the hamster. It was confirmed that taurocholate increased the maximal biliary secretory rate of the dye, while it was shown that ursodeoxycholate did not. When the bile acids were infused before sulfobromophtalein, the maximal biliary secretory rate of the dye was significantly higher under taurocholate infusion than under tauroursodeoxycholate and ursodeoxycholate infusions. Under the same conditions, the biliary bile acid output was only slightly decreased by the dye under taurocholate infusion, while it was reduced by approximately one-half under urso- and tauroursodeoxycholate infusions. These observations indicate that ursodeoxycholate is unable to increase the maximal biliary secretory rate of sulfobromophthalein (in contrast to taurocholate). It is suggested that urso- and tauroursodeoxycholate interact with sulfobromophthalein during hepatic transport and that these two bile acids may be transported by the liver by mechanisms different from those of taurocholate.

Animals↗
PubMed1994

The effects of recombinant human insulin-like growth factor I on growth hormone secretion in adolescents with insulin dependent diabetes mellitus.

OBJECTIVE: It has been proposed that low IGF-I levels and reduced IGF-I bioactivity may lead to elevated GH levels in adolescents with insulin dependent diabetes (IDDM). We have therefore studied the effects of human recombinant insulin-like growth factor I (rhIGF-I) administration on GH levels and GH secretion in adolescents with IDDM. PATIENTS: Nine late pubertal adolescents (four male and five female) with IDDM. DESIGN: A double-blind placebo controlled study of rhIGF-I administered subcutaneously in a dose of 40 micrograms/kg body weight at 1800 h. MEASUREMENTS: IGF-I and GH concentrations were measured at regular intervals throughout the study. Twenty-two hour GH secretory rates were calculated by deconvolution analysis. Overnight GH profiles were analysed by distribution analysis, and Fourier transformations were performed on both overnight GH concentrations and GH secretory rates. RESULTS: Mean IGF-I levels over the 22-hour study period were significantly elevated following rhIGF-I administration (350 +/- 26 vs 205 +/- 21 micrograms/l (mean +/- SEM), P < 0.01). Mean 22-hour GH levels were reduced following rhIGF-I administration (19.4 +/- 4.0 compared with 33.6 +/- 5.8 mU/l; P = 0.01). Distribution analysis demonstrated that the reduction in GH levels was due to changes in the proportion of values at both high and low concentrations. Deconvolution analysis also revealed a significant overall reduction in GH secretory rate following IGF-I administration (1.81 +/- 0.30 vs 2.98 +/- 0.47 mU/min, P = 0.01) which was still apparent during the final 5.5 hours of the study period (1.51 +/- 0.30 vs 2.76 +/- 0.61 mU/min, P = 0.02). The dominant periodicity of GH secretory episodes as determined by Fourier transformation was between 120 and 180 minutes after both IGF-I and placebo. CONCLUSIONS: In late pubertal adolescents with IDDM the rise in IGF-I levels following rhIGF-I administration in a subcutaneous dose of 40 micrograms/kg body weight leads to a significant reduction in GH levels and GH secretory rate. The reduction in GH secretion is due to changes in pulse amplitude rather than frequency. A reduction in GH secretion was apparent at the beginning and also towards the end of the 22-hour study period.

Adolescent↗
PubMed1975

Electrophysiology of the frog gastric mucosa with sufficient CO2.

Changing from 5% CO2 in the serosal solution only to 10% CO2 on both sides doubles the acid secretory rate of the bullfrog stomach (as shown previously) and raises the transmural potential difference, although the short-circuit current is not changed. The secretory overshoot on reoxygenation after anaerobiosis, observed in 5% CO2, is virtually eliminated in 10% CO2, as predicted by the diffusion model which explains the secretory rate increase. It was found that the rate of rise of the secretory rate during anoxia was identical in the 2 conditions, which explains the increased secretory lag in 10% CO2 and suggests an interesting limitation on the rate with which acid secretion can be activated. During anoxia in 10% CO2, but not in 5% CO2, there occurs a sudden drop in PD to a slightly negative value associated with a fall in tissue resistance. This effect occurs under SCN-inhibition and thus seems unrelated to H+ transport per se. A working model is presented which can explain some of the events surrounding the sudden potential drop.

Animals↗
PubMed1988

Does anxiety reduce the secretion rate of secretory IgA in saliva?

The effects of anxiety, depression and psychological stress on the secretion rate of salivary immunoglobulin (Ig)A were examined in a cross-sectional study of 114 registered nurses. A single, timed (five minutes) sample of whole unstimulated saliva was collected from each nurse; at the time of collection, psychosocial data for each nurse were collected by questionnaire. Nurses who reported more frequent episodes of anxiety had significantly lower mean secretion rates of salivary IgA than did nurses who reported only occasional episodes of anxiety. The concentration of secretory IgA in saliva decreased as the salivary volume increased. It was not possible to demonstrate whether anxiety influenced IgA secretion in saliva independently of its effects on salivary flow.

Adult↗
PubMed1984

Pituitary and adrenal function in epileptic patients.

ACTH and cortisol were measured simultaneously in plasma samples obtained every 5 min from subjects at two different diurnal times. In the first study adrenocorticotropic hormone (ACTH) mean concentration and secretory rate were elevated in anticonvulsant drug-treated temporal lobe epileptic patients in comparison to anticonvulsant drug-treated patients with pseudoseizures. Cortisol mean concentrations and secretory rate were similar in these groups of subjects. In the second study, mean ACTH concentration and secretory rate were higher in temporal lobe epileptic patients than in normal controls. Both measures of ACTH secretion were similar in post-temporal lobectomy patients and normal controls. Mean cortisol concentration and secretory rates were highest in the temporal lobe epileptic patients, lowest in normal controls, and intermediate in post-temporal lobectomy patients. We conclude that ACTH and cortisol secretion is abnormal in temporal lobe epileptic patients. Temporal lobectomy restores abnormal ACTH secretion to normal whether or not seizures are controlled. The absence of ACTH changes in the pseudoseizure patients suggests that these changes are not drug induced. Cortisol secretion is similar in temporal lobe epileptic patients and pseudoseizure patients, suggesting a direct effect of the drugs upon the adrenal cortex.

Adolescent↗
PubMed1990

Effects of phorbol esters and secretin on pancreatic juice secretion in the anaesthetized rat.

1. An investigation was made of the effects of phorbol esters, 12-O-tetradecanoylphorbol acetate (TPA) and secretin on pancreatic juice secretion in the anaesthetized rat. TPA (10(-12)-10(-8) mol/kg body wt) evoked marked dose-dependent increases in secretory rate and total protein output. 2. An inactive phorbol ester (4 alpha-phorbol-12-13-didecanoate; 4 alpha PDD) had no effect on the secretory rate but increased total protein output compared to saline control animals. 3. When TPA was administered in combination with the protein kinase C inhibitor, Polymyxin B (10(-8) mol/kg body wt) both secretory rate and protein output were significantly reduced (P less than 0.001) compared to TPA alone. 4. Secretin (50-1600 pmol/kg body wt) increased both pancreatic juice flow and total protein output in a dose-dependent manner. 5. Simultaneous administration of secretin (50-1600 pmol/kg body wt) and TPA (10(-10) mol/kg body wt) resulted in a marked attenuation in the secretin-induced secretory rate while secretin-evoked protein output was unaffected. 6. The results indicate that protein kinase C activation is associated with pancreatic juice secretion and it may also modulate secretin-induced pancreatic juice flow in the anaesthetized rat.

Anesthesia↗
PubMed1985

Differential regulation of activation, clonal expansion, and antibody secretion in human B cells.

Limiting dilution analysis, hemolytic plaque assay, and ELISA procedures were used to study the recruitment, clonal expansion, and antibody secretion in human TNP-specific B cells activated in the presence of TNP-ovalbumin (TNP-OA), pokeweed mitogen (PWM), or regulatory T cells. TNP-OA-responsive, hapten-specific PFC precursor cells occupy approximately 0.5% of all sIgM+/sIgD+ B cells in cord blood, bone marrow, peripheral blood, and tonsil. The PWM-responsive, hapten-specific PFC precursor pool is 70 to 90% smaller and does not express sIgD. Antigen-reactive B cells go through a minimum of three divisions in culture (six to nine PFC per clone), and antibody secretory rates of about 10(4) molecules IgM/cell/hr are achieved. In contrast, PWM-induced clone sizes were at least 60 PFC per clone, with antibody secretory rates of approximately 6 to 7 X 10(4) molecules IgM/cell/hr. Addition of high-dose carrier-primed suppressor T cells to limit dilution cultures reduced PFC precursor cell recruitment by up to 99%. However, in the few clones escaping from suppression, both clonal expansion and antibody secretory rates were much higher than in suppressor cell-free cultures, generating 30 to 60% of the antibody secreted in controls but with consequently much more restricted clonal diversity. When limiting dilution cultures were compared with standard microcultures of 2 X 10(5) cells, both clonal expansion and antibody secretory rates were much lower than expected, with a culture efficiency calculated to be 10 to 20% of that in low-density cultures. Our data suggest that the B cell subsets activated by antigen and by mitogen differ in their abilities for clonal expansion and antibody secretion. The hapten-specific and -responsive B cell family is expressed early in ontogeny, and in adults it is distributed evenly throughout the body. These limiting dilution experiments revealed that the primary effect of regulatory T cells is a drastic reduction in clonal diversity, and much less a mere reduction in overall response magnitude.

Aging↗
PubMed2004

[Comparison of prevalence rates of secretory otitis media in Hong Kong Chinese children with western populations].

OBJECTIVE: To investigate the prevalence rate of secretory otitis media (SOM) in Hong Kong Chinese children and further compare the results with the western studies. METHODS: From 1995 to 1998, primary schools, kindergartens and nurseries were selected by stratified randomization in Hong Kong of China. Six thousand eight hundred and seventy-two children of age 2 to 7 were examined on-site in the school premises by the otolaryngologist and audiologist with otoscope and tympanometry respectively. In order to achieve standardization comparisons, our raw data were retrieved and the prevalence rates were recalculated according to the various diagnostic criteria set by the western studies. RESULTS: The prevalence of SOM in the age-groups 2-3, 4-5 and 6-7 of the present study ranged from 5.2% to 21.6% if criteria were set to clinical otoscopic findings and ranged from 7.3% to 30.7% if criteria were based on tympanometric findings. The variations in the diagnostic criteria with tympanometric findings also lead to a deviation of prevalence rates with the same set of data. Regardless of the criteria set for investigations, there are no significant differences between our findings and those of the western studies with the same age groups. Prevalence rates decrease as age increases. CONCLUSIONS: The prevalence rates of SOM in Chinese children of age 2-3, 4-5 and 6-7 in Hong Kong are not significantly different from those reported in the literature of the West.

Acoustic Impedance Tests↗
PubMed1992

A quantitative estimation of growth hormone secretion in normal man: reproducibility and relation to sleep and time of day.

Recent reports, based on measurements of plasma GH levels, have challenged the concept that GH secretion is dependent on sleep and not modulated by circadian rythmicity. Because plasma levels reflect not only the secretory process, but also the effects of distribution and degradation, temporal limits of active secretion and, consequently, synchrony with other physiological events cannot be accurately estimated from circulating concentrations. The present study was undertaken to examine the roles of sleep and time of day in modulating pulsatile GH secretion, using a mathematical procedure (deconvolution) allowing secretory rates to be estimated from peripheral levels. Eight young nonobese healthy men participated each in six separate 16-h studies involving either normal or delayed sleep. Plasma GH levels were measured at 15-min intervals, and GH secretory rates were calculated by deconvolution. Each individual study was preceded by one night of habituation, and sleep was polygraphically recorded in all studies. Repeated measurements of plasma insulin-like growth factor-I (IGF-I) were performed in all subjects. Deconvolution revealed the existence of approximately 20% more GH pulses than detected in the plasma profiles. Large peaks of plasma GH concentrations often reflected the occurrence of a succession of secretory pulses. The total amount of GH secreted varied 10-fold across individual studies, but the within-subject variability (32%) was less than half the across-subject variability (65%). IGF-I levels were also more reproducible for a given subject than across subjects (11% vs. 36% variability) and did not correlate with the amount of GH secreted. During normal waking hours, the GH secretory rate was similar in the evening and the morning. This secretory rate was doubled during wakefulness at times of habitual sleep and tripled during sleep, even when sleep was delayed until 0400 h. A pulse starting within 30 min after sleep onset was present in all profiles with normal sleep and in 13 of 16 profiles with delayed sleep. The amount of GH secreted in response to sleep onset was tightly correlated with the level of secretion during wakefulness (r = 0.92). Almost 70% (57 of 83) of the pulses occurring during sleep were associated with slow wave (SW) stages. The amount of GH secreted in SW-associated pulses was correlated with the amount of SW occurring during the pulse, even when sleep-onset pulses were not considered. We conclude that in normal adult men, the amount of GH secretion and the levels of IGF-I are more reproducible within than across individuals.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Selective muscarinic sensitivity in perfused pancreata of obese Zucker rats.

Insulin secretion was evaluated in response to the muscarinic agonist, bethanechol, and to the antagonist, atropine, in three-month-old female homozygous lean (Fa/Fa) and obese (fa/fa) Zucker rats, using an in vitro pancreas perfusion. Three doses of bethanechol were used (0.5, 5 or 50 microM). Bethanechol at 50 microM concentration had a significant potentiating effect on glucose-induced insulin secretion in pancreata from both lean and obese rats. There was no effect of atropine (25 microM) on insulin secretion in pancreata from either lean or obese rats. In another study, the perfusate used contained glucose at 75, 125 or 200 mg/dl for the entire 60 min period. Perfusate, with or without bethanechol (50 microM), was infused from 21-40 min, using a side-arm syringe. In general, bethanechol significantly increased insulin secretory rates in both lean and obese rats. Since the pancreas of obese rats secretes more insulin to the same glucose concentration than the pancreas of lean rats, we compared changes in insulin release due to bethanechol in obese and lean rats having comparable basal insulin secretory rates during the 11-20 min period. To produce comparable insulin secretion, glucose levels in the perfusate were kept lower in the obese group (75 mg/dl). In the comparably secreting lean group, a glucose level of 200 mg/dl was required. We also compared changes in insulin secretory rate due to bethanechol stimulation between groups with comparable insulin secretory rates during the 21-40 min period in the control groups, i.e. 75 mg/dl glucose in the obese group vs. 125 mg/dl glucose in the lean group.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1987

Effects of ion transport inhibition on rat mandibular gland secretion.

The effects of substituting gluconate for extracellular Cl, and of treatment with various ion transport blockers, on cytosol pH (pHi) and secretion by the acetylcholine stimulated rat mandibular gland were studied in vitro. Gluconate replacement increased pHi from 7.12 +/- 0.02 to 7.27 +/- 0.04, caused secretory rate to fall by 75%, and increased salivary HCO3 from 14 +/- 0.9 mmol/L to 67 +/- 1.5 mmol/L. Furosemide (1 mmol/L), which blocks Na-K-2Cl symports and Cl-HCO3 antiports, had effects similar to those of gluconate replacement, except that secretion was reduced only by 59%. Bumetanide (1 mmol/L), which blocks only Na-K-2Cl symports, caused a 67% reduction in secretion rate, but it had little effect on pHi and caused only a small rise in salivary HCO3 concentration. SITS (1 mmol/L), which blocks Cl-HCO3 antiports, increased pHi to 7.26 +/- 0.03 and induced a small rise in the secretory rate. Methazolamide and acetazolamide (1 mmol/L), both of which inhibit carbonic anhydrase and may also block anion channels, increased pHi to 7.43 +/- 0.02 and 7.20 +/- 0.03, respectively, but had no effect on secretory rate, and reduced salivary HCO3 slightly. Ba (3 mmol/L), tetraethylammonium (10 mmol/L), and decamethonium (5 mmol/L) all caused marked but reversible reductions in secretory rate, consistent with the known actions of these agents on K channels. Ba, however, also appeared to act as a Ca antagonist, an action that it seemed to share with Mn ions (5 mmol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1976

Progesterone secretion by adrenal glands of hamsters and comparison of ACTH influence in rats and hamsters.

Studies were designed to determine a) if adrenal glands of hamsters secrete progesterone (PROG), b) the effects of adrenocritocotropin (ACTH) administration on adrenocortial function of rats and hamsters under the surgical conditions necessary for collection of adrenal venous blood from the left renal vein, and c) the effects of blood loss during sample collection. PROG was quantitated by the competitive protein-binding method after extraction and separation by sephadex LH-20 column chromatography. The presence of interfering quantities of androstenedione necessitated two column chromatographic steps. Glucocorticoids (11-OHCS) were determined fluorometrically. PROG was detected in adrenal venous plasma of female hamsters. The PROG concentration and secretory rate were 91 +/- 12 ng/ml and 4 +/- 1 ng/min, respectively, while the peripheral plasma level of the same animals was 2 +/- 0.2 ng/ml, indicating that the adrenal glands of female hamsters are capable of secreting PROG. ACTH administration increased PROG secretory rates in both hamsters (3 +/- 1 to 14 +/- 3 ng/min) and rats (62 +/- 9 to 152 +/- 32 ng/min) on estrus, as well as increasing the 11-OHCS secretory rate of hamsters (16 +/- 1 to 33 +/- 4 ng/min), but not of rats. The greater increase in PRCC than in 11-OHCS secretion may be related to excess PROG formation relative to the capacity of the 17alpha- or 21-hydroxylating enzyme systems. The adrenal venous PROG concentration and secretory rate of female hamsters infused with 10% dextran while collecting adrenal venous blood did not differ significantly from those of the non-infused animals, suggesting that this amount of blood loss (1 ml) does not influence PROG secretion.

Adrenal Glands↗
PubMed1975

Oxygenation of frog gastric mucosa in vitro.

We have recently shown that 5% CO2/95% O2 in the serosal bathing solution, with 100% O2 in the mucosal solution, results in CO2-diffusion limitation of acid secretion in bullfrog gastric mucosa. Changing to 10% CO2/90% 02 on both surfaces doubles the acid secretory rate. We calculate that, were the rate of oxygen consumption to increase significantly as a result of secretory stimulation, the tissue would now be oxygen limited. This prediction is tested by raising the P02 by increasing the total pressure in a hyperbaric chamber. Since no change in acid secretory rate or potential difference was observed upon changing from PO2 = 0.9 to PO2 = 1.9 atm, we conclude that the tissue is not O2 limited at normal pressure. Decreasing PO2 below 0.9 atm, by contrast, decreases the acid secretory rate and raises both PD and resistance. We infer that the rate of oxygen consumption did not rise significantly when acid secretion was increased by supplying sufficient CO2.

Animals↗