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PubMed1987

Effect of periglandular ionic composition and transport inhibitors on rhesus monkey eccrine sweat gland function in vitro.

1. The effects of peritubular ions and transport inhibitors were studied on methacholine (MCH)-induced sweat secretion by the isolated, cannulated monkey palm sweat glands in vitro and on the transepithelial and basolateral membrane potential (p.d.). 2. Sweat secretory rate was a curvilinear function of peritubular Na+ and Cl- concentration. Among the anion substitutes only Br- was able to totally substitute for Cl-. Presence of HCO3- or H2PO4- in the bath was not essential. 3. Both bumetanide and furosemide inhibited sweat secretion in a dose-dependent manner with the median effective concentration (EC50) of 3 X 10(-6) and 3 X 10(-5) M, respectively. 4. Bumetanide (10(-4) M) had no significant effect on basolateral membrane p.d. but nearly abolished the transepithelial p.d. 5. Hydrochlorothiazide (HCTZ, 3 X 10(-4) M) inhibited sweat secretion by only 35%. Inhibitors of ion exchangers amiloride (10(-4) M) and DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid, 10(-4) M) lowered sweat secretion by less than 20%. 6. Removal of peritubular K+ as well as addition of 5 mM-Ba2+ also inhibited sweat rate. 5 mM-Ba2+ abolished the transepithelial p.d. and depolarized the basolateral p.d. by 26 mV, although the effects of Ba2+ on sweating and the transepithelial p.d. were only transient. 7. The data raise a possibility that either the NaCl or Na+-K+-2Cl- co-transport system or both may be involved in MCH-induced sweat secretion, whereas the role of parallel ion exchangers, if any, may be rather minor.

Action Potentials↗
PubMed1987

Naloxone evokes large-amplitude GnRH pulses in luteal-phase ewes.

Ewes were sampled during the mid-late luteal phase of the oestrous cycle. Hypophysial portal and jugular venous blood samples were collected at 5-10 min intervals for a minimum of 3 h, before i.v. infusions of saline (12 ml/h; N = 6) or naloxone (40 mg/h; N = 6) for 2 h. During the 2-h saline infusion 2/6 sheep exhibited a GnRH/LH pulse; 3/6 saline infused ewes did not show a pulse during the 6-8-h portal blood sampling period. In contrast, large amplitude GnRH/LH pulses were observed during naloxone treatment in 5/6 ewes. The mean (+/- s.e.m.) amplitude of the LH secretory episodes during the naloxone infusion (1.07 +/- 0.11 ng/ml) was significantly (P less than 0.05) greater than that before the infusion in the same sheep (0.54 +/- 0.15 ng/ml). Naloxone significantly (P less than 0.005) increased the mean GnRH pulse amplitude in the 5/6 responding ewes from a pre-infusion value of 0.99 +/- 0.22 pg/min to 4.39 +/- 1.10 pg/min during infusion. This episodic GnRH secretory rate during naloxone treatment was also significantly (P less than 0.05) greater than in the saline-infused sheep (1.53 +/- 0.28 pg/min). Plasma FSH and prolactin concentrations did not change in response to the opiate antagonist. Perturbation of the endogenous opioid peptide system in the ewe by naloxone therefore increases the secretion of hypothalamic GnRH into the hypophysial portal vasculature. The response is characterized by a large-amplitude GnRH pulse which, in turn, causes a large-amplitude pulse of LH to be released by the pituitary gland.

Animals↗
PubMed1976

[Pancreatic secretion in rats. A comparative study of basal and stimulated secretions in acute and chronic fistula conditions (author's transl)].

Two types of pancreatic fistulas were directly compared in Wistar rats, to define more accurately the differences between collecting pancreatic juice under anesthesia (acute fistula) and in awake restrained animals (chronic fistula). Basal outputs of water, bicarbonate and total protein were about then times larger in chronic than in acute animals; they could be larger than the maximal secretory rate in anaesthetized rats. As a corollary, the chronic preparation was less sensitive to ecbolic and hydrelatic stimulations, with respect to basal levels. It is concluded that chronic fistula rats display a highly stimulated state of pancreatic secretion, probably due to the potentiation of several neurohumoral factors. Whatever this stimulation originates from, it renders the model less suitable for studies on ancreatic stimulating agents. On the contrary, anaesthetized rats displayed a low secretion more responsive to stimulating agents.

Acetylcholine↗
PubMed1993

Thyrotropin-releasing hormone and gonadotropin-releasing hormone-associated peptide modulation of [Ca2+]i in human lactotrophs.

The effect of thyrotropin-releasing hormone (TRH) and gonadotropin-releasing hormone-associated peptide (GAP) was studied on both secretion and intracellular free Ca2+ concentrations ([Ca2+]i) in human pituitary cells cultured from prolactin (PRL)-secreting tumors. Secretion was measured during a 30-min incubation period and we used a microspectrofluorimetric method in individual cells and indo-1 as the fluorescent probe. TRH (10(-8) M) significantly increased PRL release in five out of the six cell populations. In these five cases, more than 68% of individual cells responded to TRH by an increase in [Ca2+]i. No significant increase in PRL secretion was found in another culture in which TRH increased [Ca2+]i in only 37% of the cells. The effect of GAP (10(-7) M) was studied in five cell populations. In three of them, a decrease of 20% to 51% of the PRL basal secretory rate was observed under GAP. GAP inhibited [Ca2+]i in respectively 59%, 46% and 94% of the cells from these cultures. The inhibitory effect of GAP was blocked by a pertussis toxin (PT) pretreatment which demonstrates the involvement of a PT-sensitive G-protein in GAP action. In two other cultures, GAP did not significantly alter PRL secretion or individual cell [Ca2+]i. These observations suggest that GAP might play a role in the control of PRL secretion in the human.

Adenoma↗
PubMed1976

Species differences in insulin secretory responses during hemorrhagic shock.

Insulin secretory rates (ISR) during intravenous glucose tolerance tests (IVGTT's) were measured in six dogs subjected to hemorrhagic shock and were compared to ISR's from five monkeys subjected to shock of comparable severity. ISR's also were measured in normotensive control dogs and monkeys subjected to the same blood sampling protocol. A sixfold increase in ISR occurred in shocked dogs after glucose loading; however, no ISR response occurred in monkeys subjected to hemorrhage. It is concluded that marked species differences exist in the insulin-glucose metabolic responses to shock. In addition, the dog would appear to be an inappropriate experimental animal as applied to trauma-insulin metabolism in man.

Animals↗
PubMed1990

Neuroendocrine correlates of premenstrual syndrome: changes in the pulsatile pattern of plasma LH.

Some studies suggest that patients suffering from premenstrual syndrome (PMS) may be affected by an endogenous opioid dysfunction. Since opioids are the main modulators of the pulsatile LH secretion, we evaluated plasma LH pulsatility in 13 patients with PMS (aged 33.1 yr) and in six asymptomatic control volunteers (aged 31.5 yr), in the late luteal phase (-7, -5 days before their next menses). The patients were prospectively evaluated for two menstrual cycles with the Menstrual Distress Questionnaire; the main symptoms which worsened during the premenstrual period were mood swings and water retention. The pulsatility of plasma LH secretion was studied by collecting blood samples every 10 min for 12 hr, starting at 0800h. The presence of LH pulses was estimated using the program DETECT on the raw data. This program also allows the computation of the instantaneous secretory rate (ISR). Ovulation was ascertained in all the controls and in nine PMS patients by means of urinary LH assay and luteal progesterone (P) determination. The remaining four patients did not ovulate. Both the ovulatory and the anovulatory PMS patients had an increased number of LH pulses/12 hr (10.3 +/- 2.4 and 11.5 +/- 4.4, mean +/- SD, respectively) in comparison with the controls (7.0 +/- 1.3 pulses, p less than 0.01), together with a reduced amplitude and duration. Similar findings were obtained with the ISR computation. Plasma P levels were similar in both the ovulatory patients and controls. The increased frequency and reduced amplitude of LH pulses in the PMS patients most likely reflect a dysfunction of hypothalamic Gn-RH release, possibly linked to a reduction of opioid inhibition.

Adult↗
PubMed1994

Human acoustic neuromas secrete interleukin-6 in cell culture: possible autocrine regulation of cell proliferation.

Interleukin-6 (IL-6) secretion by cell cultures of human acoustic neuromas was examined. Secretory rates varied from 0.02 to 5.4 ng/10(5) cells per 4 days, depending on the tumor. The IL-6 immunoreactivity eluted from a Sephadex G-100 column in a major peak corresponding to an M(r) of 30,000 and a lesser peak corresponding to an M(r) of 50,000. Western blot analysis revealed three IL-6 immunoreactive bands with M(r)s corresponding to 53,000, 29,000, and 24,000. Tumor necrosis factor-alpha, interleukin-1-beta, and cholera toxin all stimulated IL-6 secretion. An antisense phosphorothioate oligonucleotide against IL-6 messenger RNA inhibited both [3H]thymidine uptake and IL-6 secretion by acoustic neuroma cells in culture. In addition, [3H]thymidine uptake was inhibited by a specific polyclonal antibody against IL-6. We conclude that human acoustic neuroma cells produce and secrete IL-6, which may act in an autocrine manner to stimulate cellular proliferation.

Adult↗
PubMed1994

Intrinsic secretory characteristics of luteinizing hormone and prolactin episodic release during pubertal development.

The intrinsic characteristics of LH and prolactin (PRL) episodic secretion were evaluated in a group of 18 children (8M and 10F). The children were divided into two groups according to the Tanner stage: Group A (Tanner < or = 1, N = 7, 3M and 4F, 6-10 years of age) and group B (Tanner 2-3, N = 11, 5M and 6F, 9-11 years of age). A pulsatility study of 4 h, sampling every 10 min, was carried out in all children. LH and PRL plasma levels were assayed by IFMA and RIA respectively. LH and PRL secretory episodes were then identified on plasma determinations using the program DETECT. Instantaneous secretory rates (ISR) were then computed for both LH and PRL using the specific algorithm within the DETECT program. Plasma LH levels were different between the two groups of children. Group A children showed undetectable LH plasma levels (below the minimal detectable dose of 0.1 mIU/ml), while group B demonstrated LH plasma levels in the normal range of values for age and sexual development (1.5 +/- 0.3 mIU/ml, mean +/- SEM). LH pulse frequency for group B was 3.2 +/- 0.4 peaks/4 h. No significant differences in mean plasma PRL levels, pulse frequency and pulse amplitude were observed between the two groups of children. Computation of ISR for LH (group B only) and PRL (both groups) identified the intrinsic episodic characteristics of the two hormones. No significant differences in LH and PRL pulse frequencies were observed when comparing the results estimated on ISR with those estimated on plasma concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1975

Reversibility of effects of very hypotonic fluids on in vitro frog gastric mucosa: a functional and morphological study.

Functional and morphological properties of the in vitro frog gastric mucosa were studied during and after exposure to very hypotonic (approximately 25 mOs M) solutions. Within 20 min the acid secretory rate decreased to zero, but it returned to normal levels after isotonic fluids had been restored. The potential difference (PD) dropped within the first minutes after the exposure to hypotonic solutions, and became inverted. Following the return of isotonic conditions the PD increased to levels higher than in the controls. The electrical resistance increased about 10-fold during the hypotonic period, but decreased to near normal values when isotonic conditions were restored. By light and electron microscopy the cells of the hypotonic mucosae appeared greatly swollen, and the alterations were assessed by morphometric methods. The gland lumina were almost obliterated, and the lamina propria was reduced to about 63% of its former volume. After the return to isotonic conditions normal morphology was restores. It is conceivable that the great increase in resistance duroing the hypotonic period was caused by the occlusion of the gland lumina. Quantitative analyses of the Na, K, and Cl tissue concentrations indicated a large loss of these ions during the hypotonic state. Presumably the epithelial cells in the hypotonic mucosae avoid bursting by rapidly letting large numbers of ions exit, which results in a celulular osmolarity close to that of the bathing fluids.

Animals↗
PubMed1983

Effects of trifluoperazine on renin secretion of rat kidney slices.

It has been suggested recently that calmodulin acts as an intracellular "Ca-receptor," and that many Ca-dependent cellular activities are mediated in some manner by Ca-calmodulin. The renin-secretory activity of juxtaglomerular cells appears to be inversely related to intracellular Ca concentration (Ca); if Ca-calmodulin is the mediator in the secretory process, it follows that secretory rate should be inversely related to Ca-calmodulin activity. The purpose of these experiments was to determine the effects of trifluoperazine, an inactivator of Ca-calmodulin, on renin secretion of rat kidney slices. Over the range 10(-6) to 10(-4) M, trifluoperazine produced a concentration-dependent increase in renin release. As assessed by lactate dehydrogenase release, the trifluoperazine-induced increase in renin release cannot be attributed to increased cell membrane permeability to proteins. Thus, trifluoperazine stimulated renin secretion in a concentration-dependent manner. This is consistent with an inverse relation between Ca-calmodulin activity and renin secretion. However, in the presence of trifluoperazine, isoproterenol still stimulated and antidiuretic hormone, angiotensin II, high extracellular K concentration, ouabain and vanadate still inhibited renin secretion. Provided these stimulatory and inhibitory effects are associated with decreased and increased Ca, respectively, these observations are inconsistent with the hypothesis that the effects of Ca, on renin secretion are mediated by changes in Ca-calmodulin activity, since increases in Ca promote rather than attenuate the binding of trifluoperazine to calmodulin. It is concluded that trifluoperazine-stimulated renin secretion is mediated by a decrease in Cai produced by inhibition of Ca influx and/or stimulation of Ca efflux and/or sequestration.

Animals↗
PubMed1984

Bombesin stimulates insulin secretion by a pancreatic islet cell line.

The amphibian tetradecapeptide, bombesin (BBS) has been shown to stimulate insulin secretion both in vivo and by pancreatic islet cells in vitro. To determine whether BBS can act directly on pancreatic beta cells, we examined its effects on insulin secretion by HIT-T15 cells (HIT cells), a clonal islet cell line. Addition of 100 nM BBS to HIT cells stimulated insulin release 25-fold within 30 sec. The rapid stimulatory effect of BBS on insulin release was short-lived: the secretory rate returned to basal levels after 90 min of BBS treatment. The decrease in the rate of insulin release in the continued presence of BBS was due not to depletion of intracellular insulin stores but to specific desensitization to this peptide. Stimulation of insulin secretion by BBS was dose dependent with an ED50 value (0.51 +/- 0.15 nM) similar to the concentration of BBS-like immunoreactive material in rat plasma. Five BBS analogs, including porcine gastrin-releasing peptide, were as powerful as BBS in stimulating insulin release. The relative potencies of the analogs tested indicated that the COOH-terminal octapeptide sequence in BBS was sufficient for stimulation of release. In contrast, 14 peptides structurally unrelated to BBS did not alter insulin secretion. BBS action was synergistic with that of glucagon; insulin secretion in the presence of maximal concentrations of both peptides was greater than the additive effects of the two peptides added individually. Somatostatin inhibited BBS-stimulated release by 69 +/- 1% with an ID50 value of 3.2 +/- 0.3 nM. These results show that BBS stimulation of insulin secretion by a clonal pancreatic cell line closely parallels its effects in vivo and support the hypothesis that BBS stimulates insulin secretion by a direct effect on the pancreatic beta cell. The clonal HIT cell line provides a homogeneous cell preparation amenable for studies on the biochemical mechanisms of BBS action in the endocrine pancreas.

Animals↗
PubMed1990

Impaired inhibitory effects of somatostatin on growth hormone (GH)-releasing hormone stimulation of GH secretion after short term infusion.

We examined the effect of prior exposure to somatostatin (SRIH) on its inhibition of GH and TSH responses to GHRH and TRH stimulation to determine whether SRIH desensitization has physiological significance in man. Six men received GHRH (1 microgram/kg, iv) and TRH (0.3 microgram/kg, iv) 20 min after starting a saline or SRIH (5.5 ng/kg/min, iv) infusion and again 6 h later. Hormone responses were quantified by measuring the area under the curve, corrected for GH concentration at injection time. Similar results were obtained when GH responses were quantified by measuring the hormone secretory rate using the program Detect. Plasma GH and TSH responses to the two GHRH and TRH injections during saline were similar. However, the effects of prior exposure to SRIH were hormone specific. SRIH blunted GH responses to GHRH at 20 min (1609 +/- 286 micrograms/L.min vs. 451 +/- 224), but did not significantly inhibit the responses 6 h later (1422 +/- 410 micrograms/L.min vs. 1000 +/- 302). In contrast, SRIH inhibition of TSH responses to the two TRH injections was similar (first, 946 +/- 201 micrograms/L.min vs. 700 +/- 148; second, 813 +/- 175 micrograms/L.min vs. 562 +/- 66). We next used these results to study whether the previously reported attenuation of GH responses to repeated GHRH stimulation at 2-h intervals is mediated by SRIH. Eight men received GHRH (1 microgram/kg, iv) 380 min after starting a saline or SRIH (5.5 ng/kg/min, iv) infusion or 90 min after starting a primed (5 mg, iv) infusion of propranolol (80 micrograms/min, iv) and again 2 h later. As in the first protocol, GH responses to GHRH were not inhibited when preceded by a 6-h SRIH infusion. However, the 6-h SRIH infusion resulted in a partial restoration of plasma GH responses to the second GHRH injection (saline infusion: first, 1429 +/- 342 micrograms/L.min; second, 254 +/- 75; SRIH infusion: first, 1042 +/- 247 micrograms/L.min; second, 468 +/- 105). beta-Blockade by propranolol resulted in enhanced GH responses to GHRH, but did not prevent the attenuation of GH responses to the second GHRH injection (first, 1937 +/- 366 micrograms/L.min; second, 614 +/- 99). The desensitization to SRIH inhibition of GH responses to GHRH after a 6-h SRIH infusion provides evidence of physiological consequences of SRIH receptor down-regulation. The impaired GH responses to repeated GHRH stimulation are mediated at least in part by enhanced SRIH secretion, which appears independent of a beta-adrenergic mechanism.

Adult↗
PubMed1992

Cholestasis, metabolism and biliary lipid secretion during perfusion of rat liver with different bile salts.

The biological effects of bile acids depend largely upon their molecular structure. When bile acid uptake exceeds the maximal biliary secretory rate (SRm) cholestasis occurs. In order to characterize the influence of bile acid structure on its cholestatic potency we systematically studied SRm, maximal bile flow, maximal and cumulative phospholipid and cholesterol secretion with different taurine-conjugated tri-, di- and keto bile acids (Table I) in the isolated perfused rat liver. Bile acids with a high critical micellar concentration (CMC) promoted the greatest bile flow; a positive non-linear correlation between CMC and maximal bile flow was found. 3 alpha-Hydroxylated bile acids with a hydroxyl group in 6 alpha and/or 7 beta position and lacking a 12 alpha hydroxy group had a high SRm. SRm was not related to CMC or maximal bile flow, respectively. Phospholipids and cholesterol were secreted in a nearly fixed ratio of 12:1; a strong linear relationship could be observed. Cumulative phospholipid secretion over 48 min was significantly lower for non and poor micelle forming bile acids (TDHC and TUC) than for those with comparatively low CMC values (TUDC, TC, THC, THDC, TCDC) (70-140 vs. 210-450 nmol/g liver). At SRm all bile acids with good micelle forming properties showed a similar cumulative biliary lipid output. However, when biliary lipid output was related to 1 mumol bile acid secreted bile acids with a low SRm induced the highest lipid secretion (TCDC, TC). These data (1) demonstrate that a 6 alpha and/or a 7 beta hydroxy group on the steroid nucleus reduce cholestatic potency if the 12 alpha hydroxy group is absent, (2) suggest that in the case of micelle forming bile acids the total amount of phospholipids secreted in bile (depletion of cellular phospholipids) is associated with the occurrence of cholestasis whereby bile acids with a low SRm deplete the cellular phospholipid content at much lower bile acid concentrations than those with a higher SRm and (3) imply that bile acids with non and poor micelle forming properties (TDHC, TUC) presumably do not cause cholestasis (solely) by depletion of cellular phospholipids.

Animals↗
PubMed1986

Sites of resistance changes with inhibition of acid secretion in frog stomach.

The primary purpose of this study was to determine the sites of resistance changes from thiocyanate inhibition of secretion to better evaluate models of the gastric proton pump. The potential difference, resistance, and H+ secretory rate were measured with various tonicities of the secretory fluid. Thiocyanate (SCN) inhibition generally produces a resistance increase, but with nutrient Ba, the resistance is high and SCN decreases it. The latter effect is also seen with cimetidine. In the secreting fundus a hypotonic secretory solution has a small effect on resistance, but in the inhibited fundus the effect is huge, due to increase of resistance of the lumen-tubular cell pathway. With a hypotonic secretory solution, for inhibited fundus (cimetidine or omeprazole) and antrum, SCN does not decrease the resistance of the surface cells and/or the transintercellular pathways with or without Ba. The SCN resistance decrease with Ba is via the tubular cell pathway. With Ba the resistance of the nutrient membrane of the tubular cells decreases after SCN or cimetidine inhibition. The findings further support the concept that under standard conditions the resistance via the lumina and tubular cells is low and that via the surface cells and transintercellular pathways is high.

Animals↗
PubMed1987

Analysis of atrial natriuretic factor biosynthesis and secretion in adult and neonatal rat atrial cardiocytes.

Atrial natriuretic factor (ANF) is stored in atrial cardiocytes as the 126 amino acid polypeptide, proANF, which is later cleaved to the 24-28 amino acid carboxyterminal peptides, the major circulating forms. Earlier studies have demonstrated that isolated, cultured neonatal rat cardiocytes both store and secrete proANF, which can be cleaved to the smaller circulating form(s) by a serum protease. Since differences may exist between neonatal and adult cardiocytes with respect to ANF synthesis and processing, we compared the forms of ANF stored and secreted by neonatal rat cardiocytes with those of adult cells. Using four to five day cultures of isolated atrial cardiocytes prepared from the hearts of neonatal and adult rats, pulse-chase studies were performed with 35S-cysteine and 35S-methionine. Analysis of ANF stored and secreted by these cells was performed by immunoprecipitation of cell extracts and culture media using antibodies directed to either the carboxyterminus or aminoterminus of proANF followed by SDS-PAGE and autoradiography. Cell extracts from both adult and neonatal cultures were found to contain only a 17-kDa polypeptide, previously identified as proANF. The predominant form found in the culture media was also the 17-kDa peptide, with smaller quantities of its 3-kDa carboxyterminal and 14-kDa aminoterminal cleavage products. We conclude from these studies that proANF is the major form stored and secreted by both adult and neonatal cardiocytes in culture; the activity of the protease that cleaves proANF to the smaller forms found in the circulation is either attenuated or is overwhelmed by high ANF-secretory rates in these cultures. Alternatively, the ANF processing and secretory pathways may be somehow altered in culture such that proANF escapes protease cleavage. Further studies will elucidate the nature and location of this protease.

Animals↗
PubMed1998

Role of glutathione in the beneficial effect of dietary restriction on bile formation in young, mature, and old rats.

We investigated the contribution of bile salts and glutathione (GSH) to the generation of bile flow in young, mature, and old female Sprague-Dawley rats, either fed ad libitum (AL) or subjected to a 40% dietary restriction (DR), which was supplemented or not with vitamins and minerals, starting from weaning. An age-related decline in bile flow was observed in the AL group. DR increased bile flow compared to age-matched AL rats, resulting in a twofold increase in the old animals. This was associated with a statistically significantly higher biliary GSH secretion rate and a moderate increase in the bile salt secretory rate. The apparent GSH-dependent flow was significantly increased in DR groups of all ages. Hepatic GSH concentration was closely related to the GSH secretion rate. These results indicate that the increase in biliary GSH content produced by DR is the major mediator of the increased bile flow, resulting in enhanced GSH and GSH-derived thiols supply to the intestinal lumen.

Aging↗
PubMed1973

Some characteristics of the rabbit vermiform appendix as a secreting organ.

It has been confirmed that the rabbit vermiform appendix secretes spontaneously at a relatively rapid rate (1-12 ml.h(-1); 1.4+/-0.24 mul.min(-1).cm(-2)). The electrolyte composition is similar to that of ileal fluids and independent of the secretory rate. The transmural potential difference is about 12 mV, mucosa negative. Of the major electrolytes, only HCO(3) (-) is secreted grossly against its electrochemical potential difference. This finding plus the low hydraulic (or osmotic) permeability (L(p)) and high secretory pressures of the organ strongly suggest that the secretion is an active one. The passive permeability to Na(+) and Cl(-) appears to be, at most, somewhat less than for small bowel. Permeability to mannitol was estimated at 2.5 x 10(-7) cm.s(-1). On the basis of reasonable assumptions and results with luminal test solutions of differing osmolarities, it was concluded that (a) the L(p) of the appendiceal epithelium is in the lower range of values reported for small bowel and colon; (b) the L(p) is higher for osmotic absorption than for osmotic secretion; and (c) the rate of spontaneous secretion is insensitive to luminal anisotonicity over a wide range of values. But sufficiently hypotonic solutions can reverse net secretion to net absorption, more by inhibiting spontaneous secretion than increasing osmotic absorption. The rabbit vermiform appendix appears to be a useful model for the elucidation of intestinal secretory processes.

Animals↗