Biomedical subjects

C Oliver

Publications and source records attributed to C Oliver.

At least 163 records · Page 9Linked to original sources

PubMed1993

Opioid binding sites in jerboa (Jaculus orientalis) brain: a biochemical comparative study in the awake-active and induced hibernating states.

1. Using tritiated ligands [3H]DADLE, [3H]DAGO, [3H]EKC and [3H]Bremazocine, we have demonstrated the presence of delta, mu and kappa sites in brain membranes from jerboa (Jaculus orientalis), a desert rodent and a true hibernator. 2. A comparative study was realized in the case of the induced hibernating state, indicating a reduction of binding capacities during the hibernation state. 3. Using radioimmunoassay, the endogenous pentapeptide methionine-enkephalin (Met-enk) was evaluated in different areas of jerboa brain in comparison with the effect of induced hibernation on the level of Met-enk. 4. A thermodynamic analysis of the effect of temperature on the binding of opioids, indicates that the hibernating and the active state are energetically different. delta G degrees, delta H degrees and delta S degrees were calculated. A break of the Van't Hoff plot was observed in the active state at 15 degrees C, indicating a possible transition state of membranous phospholipids and/or proteins. 5. The role of phospholipids was studied, using the effect of phospholipase A2 and membrane reconstitution. Phospholipids play a key role in the opioid binding.

Animals↗

PubMed1993

Facilitation and feedback in the hypothalamo-pituitary-adrenal axis during food restriction in rats.

After 4 weeks of food restriction to 50% of ad libitum intake in rats, plasma corticosterone levels were increased, without any change in adrenal weight, and with no evidence of sympathetic nervous system activation (as measured by Tyrosine Hydroxylase and Phenylethanolamine N-Methyl Transferase activities in the adrenal gland). Plasma corticosterone levels were normalized wih the addition of 35% of the calories as sugar. The adrenocortical axis activity was therefore investigated in more detail (nycthemeral cycle of corticosterone levels, ACTH and corticosterone response to a CRF challenge) in ad libitum fed rats and in animals fed 85% or 50% of the intake of the control animals, just before switching the lights off in order to maintain the diurnal rhythm of food intake. Food restriction to 85% did not change mean plasma corticosterone levels but sharpened the peak of corticosterone measured in the evening, indicating that the adrenocortical axis is more sensitive to the endogenous signals responsible for its diurnal cycle of activity. Indeed, the ACTH response to CRF was also increased. A 50% food restriction regimen increased mean corticosterone levels and attenuated the day/night difference, with high corticosterone levels maintained throughout the day. However, the ACTH response to CRF was not different from that measured in ad libitum fed rats, but the corticosterone response was lower, confirming that the adrenal gland is hyposensitive to ACTH. The results are discussed in terms of the balance between inhibiting/activating mechanisms and endocrine/neural influences at each level of the hypothalamo-hypophyso-adrenal axis, depending on the level of food deprivation.

Adrenocorticotropic Hormone↗

PubMed1993

Effect of excitatory amino acid on the hypothalamo-pituitary-adrenal axis in the rat during the stress-hyporesponsive period.

During the postnatal period from day 2 to day 10 of life, basal and stress-induced adrenocorticotropic hormone (ACTH) and corticosterone releases are low as compared with adults. This period has been called the 'stress-hyporesponsive period', and its mechanisms are yet undetermined. In this study, we have tested the effects of substances excitatory to neuronal activity on the hypothalamic-pituitary-adrenal (HPA) axis. In 7-day-old rats, administration of the excitatory amino acid (EAA) agonists N-methyl-D,L-aspartic acid (NMA), quisqualic acid, and kainic acid (KA) induced a large increase in plasma ACTH and corticosterone concentrations. All three EAA induced a rapid and potent stimulation of ACTH release within 30 min, the effect on corticosterone secretion being weaker. KA was the more potent EAA, followed by NMA and quisqualic acid. The effect of NMA on the HPA axis was inhibited by pretreatment with a competitive antagonist to N-methyl-D-aspartic acid receptors, D,L-2-amino-5-phosphonovaleric acid. We next sought to determine which level of the HPA axis was affected by EAA administration. Several EAA (glutamic acid, N-methyl-D-aspartic acid, and KA from 10(-5) to 10(-2) M) had no stimulating action on ACTH release from 7-day-old anterior pituitary glands incubated in vitro. In vivo, the stimulating effect of NMA and KA on in vivo ACTH release was blocked after passive immunization with an anti-corticotropin-releasing hormone antiserum, but not after injection of an anti-arginine vasopressin antiserum.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗

PubMed1993

Passive immunization and hypothalamic peptide secretion.

Passive immunization is a common approach used to eliminate the biological activity of an endogenous substance by its binding to a specific antibody (Ab). Surprisingly little information has been gathered on the mechanisms involved. Moreover, the possibility that immunoneutralization could affect also the secretion of the antigen itself has been mostly ignored. To study hypothalamic neuropeptide secretion under the condition of passive immunization, labeled and unlabeled monoclonal antibody (MoAb) against arginine vasopressin (AVP) was injected intravenously. After 2 h a similar amount of 125I-MoAb was found in hypophyseal portal and peripheral (femoral artery) plasma, showing a distribution volume of 73.2 ml/kg. Assessment of the MoAb dilution in the same plasma samples from the binding studies revealed substantially higher dilutions (800-5,700 ml/kg). Such a MoAb dilution (saturation) would be attained by the binding of 130-290 pmol AVP/ml plasma. The calculated amount of plasma AVP decreased by one half within the interval from 2 to 24 h after Ab injection, similarly as did the 125I-MoAb content. Intravenous injection of polyclonal corticotropin-releasing hormone (CRH) Ab resulted in a decrease of plasma adrenocorticotropin and corticosterone levels. After 24 h the dilution of the Ab in portal plasma exceeded two times that in peripheral plasma. CRH concentrations of 0.6-2.5 pmol/ml were found by specific radioimmunoassay after its dissociation from the Ab in plasma. The CRH concentration was higher in portal than in peripheral plasma and was related to the amount of the Ab injected. CRH mRNA levels in the paraventricular nucleus were significantly increased in CRH Ab as compared with normal rabbit serum injected rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Alpha-melanocyte-stimulating hormone is present in the inferior petrosal sinuses in patients with Cushing's disease.

Plasma ACTH, beta-endorphin and alpha-melanocyte-stimulating hormone levels were evaluated in the inferior petrosal sinuses and in the periphery of 22 patients affected by Cushing's disease, 11 patients with other pituitary diseases subjected to simultaneous and bilateral inferior petrosal sinus sampling and in the peripheral blood of 15 normal subjects. In patients with Cushing's disease ACTH, beta-endorphin and alpha-melanocyte-stimulating hormone levels in the inferior petrosal sinus ipsilateral to the adenoma were significantly higher than in the periphery and in the contralateral inferior petrosal sinus (p < 0.01, p < 0.01 and p < 0.05, respectively). In patients with other pituitary diseases only ACTH and beta-endorphin, but not alpha-melanocyte-stimulating hormone levels in both inferior petrosal sinuses were significantly higher than in the periphery (p < 0.01). Furthermore, no difference was found in the peripheral blood among patients with Cushing's disease, patients with other pituitary diseases and normal subjects for ACTH and beta-endorphin level. By contrast, in patients with Cushing's disease peripheral alpha-melanocyte-stimulating hormone levels were significantly higher than in patients with other pituitary diseases and in normal subjects (p < 0.05). In conclusion, the results of the present study suggest that only in patients with Cushing's disease, but not in patients with other pituitary diseases, alpha-melanocyte-stimulating hormone is released by adenomatous pituitary corticotrophs together with ACTH and beta-endorphin.

Adolescent↗

PubMed1993

Neostigmine stimulates growth hormone-releasing hormone release into hypophysial portal blood of conscious sheep.

GH secretion is stimulated by the administration of cholinesterase inhibitors (such as pyridostigmine and neostigmine) in several species, including man. On the basis of indirect experiments, it has been postulated that this action is mediated by a decrease in hypothalamic somatostatin release. We have investigated the effect of neostigmine in sheep, since it is possible to collect hypophysial portal blood for GH-releasing hormone (GHRH) and somatostatin determination in this species under a conscious unstressed state. First, after i.v. injection of neostigmine (1 mg), a significant increase in plasma GH levels and an unequivocal potentiation of the GH response to GHRH were observed. Then, we observed that i.v. injection of neostigmine (1 mg) induced an immediate, short-lasting (30 min), and marked increase in GHRH (126.1 +/- 17 vs. 14.5 +/- 2.1 pg/ml; P < 0.01) levels in hypophysial portal blood of rams chronically implanted with perihypophysial cannulae. No change in somatostatin secretion was recorded during the same period. These data suggest that the stimulating effect of cholinergic drugs on GH secretion is mediated by stimulation of GHRH release. A direct effect of neostigmine at the level of pituitary gland is possible and may explain the potentiation of GHRH-induced GH release.

Animals↗

PubMed1993

In situ hybridization of arginine vasopressin (AVP) heteronuclear ribonucleic acid reveals increased AVP gene transcription in the rat hypothalamic paraventricular nucleus in response to emotional stress.

The regulation of anterior pituitary adrenocorticotropin hormone (ACTH) secretion during stress involves several hypothalamic neurohormones, including arginine vasopressin (AVP). In situ hybridization techniques have been used to study the regulation of neuropeptide messenger ribonucleic acids in the hypothalamus. Owing to the relatively slow time course of the changes in cytoplasmic messenger ribonucleic acid concentrations, rapid alterations in the level of neuropeptide gene transcription could not be detected. Because of its rapid processing, the nuclear level of the heteronuclear ribonucleic acid should reflect the rate of its synthesis, namely the transcription of the gene. We have used in situ hybridization with a probe complementary to a portion of an intronic sequence of the rat AVP gene to study rapid changes in the level of AVP gene transcription during emotional stress. The specificity of our technique was demonstrated by the localization of the hybridization signals in the paraventricular nucleus, the supraoptic nucleus and the suprachiasmatic nucleus, and was confirmed by the nuclear localization of the labeling. Isolation and exposure of male rats to a novel environment induced an activation of the pituitary-adrenal axis and an increase in AVP heteronuclear ribonucleic acid concentrations in the paraventricular nucleus 2 h after the onset of the stress, suggesting that an increased AVP gene transcription may play a role in the activation of the pituitary-adrenal axis in response to emotional stress.

Animals↗

PubMed1993

[Stress. Neuroendocrine aspects].

All kind of stress produce an endocrine response. These hormonal responses can serve as stress indicators. The main peripheral endocrine responses to stress are the activation of adrenal corticoids, the stimulation of Growth Hormone (GH) and prolactin secretion, and the inhibition of insulin and gonadal secretion. Except for the inhibition of insulin release, all these hormonal variations depend on the adenohypophysis activity: stimulation of Adrenocorticotrophin hormone (ACTH), GH and prolactin, and inhibition of gonadotrophins (LH-FSH) secretions. Several lines of evidence demonstrate that specific hypothalamic Neuro-hormones stimulate or inhibit the hypophysial activity in response to stress. However, due to methodological difficulties, only measurements of peripheral hormones can be used as stress indicators.

Adrenocorticotropic Hormone↗

PubMed1993

Why battering during pregnancy?

This exploratory study was designed to determine the reasons men might beat their female partners during pregnancy from the perspectives of women who had experienced this form of violence. Seventy-nine battered women were recruited by newspaper advertisement and bulletin board postings to take part in a larger study of women's responses to relationship problems. Women battered in their relationships were asked if they had ever been beaten during pregnancy. The 27 (34%) women who had a pregnancy with the abusive partner as the father and had experienced physical abuse during the pregnancy were compared with 24 (30%) women who also had been pregnant by the abuser but had not been abused during pregnancy. The only significant difference between the two groups was that the women battered during pregnancy were more frequently and severely beaten throughout the course of the relationship. Those abused during pregnancy were asked why they thought that had happened. Their answers were thematically analyzed into the categories: (1) jealousy of the unborn child; (2) anger toward the unborn child; (3) pregnancy-specific violence not directed toward the unborn child; and (d) "business as usual." Implications for nursing assessment and interventions for abuse during pregnancy are derived from this analysis.

Adult↗

PubMed1992

Pre- and post-natal ontogeny of thyrotropin-releasing-hormone in the rat spinal cord: an immunocytochemical study.

This work aimed at providing by means of immunocytochemical techniques a detailed study of the ontogeny of thyrotropin-releasing hormone (TRH) in the spinal cord of the rat. We report the first appearance of TRH-immunoreactive fibers in the ventral funiculus of thoracic and lumbar levels at embryonic day 17. At embryonic day 18, fibers penetrated the ventral gray matter towards the central canal. At embryonic day 19, the first immunoreactive fibers were seen in the intermediolateral cell column at upper thoracic levels. This region was invaded at lower thoracic levels on the day of birth. At this time, TRH-immunoreactive axodendritic synapses were observed in the ventral horn and in the intermediolateral cell column. Immunoreactivity increased in these regions until post-natal day 21 when the adult pattern of TRH immunoreactivity was established in the sympathetic nuclei and in the ventral horn. However, a transient TRH-like immunoreactivity was detected in lamina IIi of the dorsal horn between post-natal days 14 and 30: at ultrastructural level, immunoreactive varicosities were seen to establish axodendritic synapses. In conclusion, TRH is one of the earliest peptidergic systems established in the spinal cord and it presents extensive temporal and topographical similarities with the serotonergic system with which it could be colocalized.

Animals↗

PubMed1992

The rat mast cell antigen AD1 (homologue to human CD63 or melanoma antigen ME491) is expressed in other cells in culture.

Previously we reported that the mAb AD1 recognized a heavily glycosylated 50- to 60-kDa protein (AD1 Ag) sterically close to the high-affinity IgE receptor on rat basophilic leukemia (RBL-2H3) cells. The N-terminal amino acid sequence of the AD1 Ag was nearly identical to that of human CD63 (melanoma-associated Ag ME491). In this study we cloned the cDNA of AD1 Ag from a rat basophilic leukemia 2H3 cDNA library. An open reading frame of 238 amino acids was identified that contained the N-terminal 43 amino acid sequence. No evidence of a signal peptide was found. However, four predominantly hydrophobic stretches of sequence were predicted to form membrane-spanning helices, and three putative N-glycosylation sites were identified. The AD1 Ag and CD63 were highly conserved between rat and human, suggesting that the sequence of this protein is important for its function. By immunostaining various rat tissues, the AD1 Ag was found localized to mast cells. However, it was located to lysosomes, secretory granules and the plasma membrane of RBL-2H3 cells and to lysosomes and plasma membrane of many other cultured cell lines. The AD1 Ag could be induced by placing cells in culture. Fibroblasts and hepatocytes freshly isolated from rat embryos stained very weakly for AD1 Ag; however, after 24 to 48 h in culture they were strongly positive. This increase in the expression of the AD1 Ag was accompanied by an increase in detectable RNA message. Therefore, AD1/ME491/CD63 Ag is a mast cell marker in tissue, but is also associated with other cells in culture.

Amino Acid Sequence↗

PubMed1992

Adherence of rat basophilic leukemia (RBL-2H3) cells to fibronectin-coated surfaces enhances secretion.

Rat basophilic leukemia (RBL-2H3) cells are a useful in vitro model for studies of mast cells and basophils. We examined the adherence of RBL-2H3 cells to different extracellular matrix proteins and the effect of such attachment on secretion. The cells bound to fibronectin-coated surfaces with maximum binding by 1 h at 37 degrees C. There was less attachment to laminin, collagen type I, and collagen type IV. There was no adherence to uncoated surfaces or in the absence of Ca2+. Binding to fibronectin was blocked by a synthetic peptide containing the sequence Arg-Gly-Asp. Therefore, the binding of RBL-2H3 cells to fibronectin may be mediated by surface molecules that belong to the integrin family. Adherence to fibronectin-coated surfaces resulted in cell spreading, a reorganization of the cytoskeletal elements, and a redistribution of the secretory granules. Attachment to fibronectin also dramatically enhanced high affinity IgE receptor-mediated histamine release. This enhancement was maximum by 1 h of adherence and lasted for at least 6 h. There was also enhanced secretion by the Ca2+ ionophore A23187. Thus, adherence to fibronectin can enhance both receptor and non-receptor-mediated release. Addition of soluble fibronectin to RBL-2H3 cells in suspension had no effect on secretion. Therefore, enhanced histamine release required cell attachment to immobilized fibronectin. These results suggest that secretion from mast cells/basophils may be modulated by their interaction with the extracellular matrix.

Animals↗

PubMed1992

Inhibition of IgE binding to RBL-2H3 cells by a monoclonal antibody (BD6) to a surface protein other than the high affinity IgE receptor.

A mAb was isolated (mAb BD6) that recognized a surface glycoprotein on rat basophilic leukemia cells (RBL-2H3). The antibody bound to 2 x 10(6) molecules/cell and specifically blocked IgE binding (50% inhibition with 3.48 +/- 0.51 micrograms/ml; mean +/- SEM), although neither IgE nor anti-high affinity IgE receptor (anti-Fc epsilon RI) mAb blocked mAb BD6 binding to the cells. mAb BD6 did not affect the rate of dissociation of cell-bound IgE, nor did it induce or inhibit the internalization of IgE. mAb BD6 did not release histamine. However, it did cause rapid spreading of the cells. By 1 h the cells had retracted to a spherical shape with their surface covered with membranous spikes, and they could easily be detached from the tissue culture plate. These changes differed from those observed after Fc epsilon RI activation. mAb BD6 immunoprecipitated a complex of two proteins, 38 to 50 kDa and 135 kDa from 125I-surface labeled rat basophilic leukemia cells that are not subunits of Fc epsilon RI. Chemical cross-linking studies showed that these molecules are associated on the cell surface. By immunoblotting, mAb BD6 reacted with a 40-kDa protein. Therefore, mAb BD6 binds to a surface protein that is close to the Fc epsilon RI and sterically inhibits 125I-IgE binding.

Animals↗

PubMed1992

Distribution of thyrotropin-releasing hormone in the rat spinal cord with special reference to sympathetic nuclei: a light- and electron-microscopic immunocytochemical study.

This paper deals with the distribution of thyrotropin-releasing hormone-like immunoreactivity in the spinal cord of the rat, and particularly in the sympathetic nuclei, at light and electron microscopic levels. In the dorsal horn, the inner part of laminae II and III displayed thin thyrotropin-releasing hormone immunoreactive profiles. Electron microscopy revealed small immunoreactive varicosities which made synaptic contact with small dendrites or dendritic spines. Dense thyrotropin-releasing hormone-like immunoreactivity was observed in all sympathetic nuclei (nucleus intermediolateralis pars fascicularis and principalis, nucleus intercalatus and dorsal commissural nucleus) except the nucleus intercalatus pars ependymalis. Electron microscopy showed many immunoreactive varicosities which were often in synaptic contact with dendrites (proximal or distal), rarely with perikarya and never with axons. Sometimes, the same immunoreactive varicosity made axodendritic contacts with two dendrites and, conversely one dendrite was sometimes synaptically contacted by two or more immunoreactive varicosities. The ventral horn displayed a diffuse thyrotropin-releasing hormone-like immunoreactivity except for the cremaster nucleus (at lumbar level) which was densely outlined by immunoreactive profiles. Occasionally a large cell body in lamina IX (a putative motoneuron) was outlined by immunoreactive profiles but ultrastructural studies revealed very few immunoreactive axosomatic synapses, while immunoreactive symmetrical or asymmetrical axodendritic synapses were observed. The present study clearly confirms the existence of thyrotropin-releasing hormone immunoreactive synapses, thus substantiating the physiological role of this hormone in the spinal cord.

Animals↗

PubMed1992

Adrenocorticotropic hormone and beta-endorphin concentrations in the inferior petrosal sinuses in Cushing's disease and other pituitary diseases.

Aim of the present study was the evaluation of ACTH and beta-endorphin-like-immunoreactivity (beta-ELI) in the inferior petrosal sinuses (IPS's) and in the peripheral blood of patients with Cushing's disease (Group 1), with GH- or PRL-secreting adenomas or nontumoral hyperprolactinemia (Group 2). These patients had undergone selective and bilateral simultaneous IPS sampling for diagnostic purposes or for neurosurgical indications. In the patients of Group 1, ACTH and beta-ELI levels were higher in the IPS ipsilateral than in the contralateral to the adenoma and in the periphery (p < 0.001). In the patients of Group 2 ACTH and beta-ELI levels were higher in the IPS's than in the peripheral blood (p < 0.001) and, in the 9 patients with GH- or PRL-secreting adenomas, they were higher in the IPS ipsilateral than in the contralateral to the adenoma and in the periphery (p < 0.05). A significant correlation exists between ACTH and beta-ELI in the periphery (p < 0.01; r = 0.72), in the IPS ipsilateral (p < 0.05; r = 0.54) and contralateral (p < 0.01; r = 0.66) to the adenoma in Group 1, but not in Group 2. In conclusion, higher beta-ELI levels were detected in the IPS's than in the peripheral blood not only in patients with Cushing's disease but also in those with other pituitary diseases not involving ACTH secretion. The absence of correlation between ACTH and beta-ELI in patients not bearing Cushing's disease suggests that in these conditions corticotrophs release ACTH and beta-endorphin in an independent manner.

Adenoma↗

PubMed1992

Acute changes in growth hormone-releasing hormone secretion after injection of BIM 23014, a long acting somatostatin analog, in rams.

BIM 23014 is a somatostatin analog displaying an increased biological half life due to resistance to enzymatic degradation. This peptide inhibits GH release directly at the level of pituitary somatotrophs. In addition, an action of BIM 23014 at the level of the hypothalamus is possible since somatostatinergic fibers and receptors have been identified on GH-RH neurons. To evaluate the effect of BIM 23014 on GH-RH secretion, hypophysial portal blood (HPB) was continuously collected in conscious sheep. Twelve rams (40-45 kg, 9-month-old) with chronically implanted perihypophysial cannulae were i.v. injected with BIM 23014 (1 mg) or saline. HPB and jugular blood were collected for 3-5 hours before and after the injection for the determinations of GH-RH and GH concentrations respectively. The acute injection of BIM 23014 induced a rapid decrease of plasma GH within the first two hours. Simultaneously, GH-RH in HPB decreased significantly. After reaching a nadir, GH concentrations increased to values greater than baseline. A similar rebound in GH-RH levels in HPB was also observed. These data indicate that BIM 23014 acts at the level of GH-RH hypothalamic neurons, in addition to its well-know effect on the pituitary gland.

Animals↗

PubMed1992

Binding of monoclonal antibody AA4 to gangliosides on rat basophilic leukemia cells produces changes similar to those seen with Fc epsilon receptor activation.

The mAb AA4 binds to novel derivatives of the ganglioside Gd1b on rat basophilic leukemia (RBL-2H3) cells. Some of the gangliosides are located close to the high affinity IgE receptor (Fc epsilon RI), and binding of mAb AA4 inhibits Fc epsilon RI-mediated histamine release. In the present study, mAb AA4 was found to bind exclusively to mast cells in all rat tissues examined. In vitro, within 1 min of mAb AA4 binding, the cells underwent striking morphologic changes. They lost their normal spindle shaped appearance, increased their ruffling, and spread over the surface of the culture dish. These changes were accompanied by a redistribution of the cytoskeletal elements, actin, tubulin, and vimentin, but only the actin was associated with the membrane ruffles. Binding of mAb AA4 also induces a rise in intracellular calcium, stimulates phosphatidyl inositol breakdown, and activates PKC. However, the extent of these changes was less than that observed when the cells were stimulated with antigen or antibody directed against the Fc epsilon RI. None of these changes associated with mAb AA4 binding were seen when the cells were exposed to nonspecific IgG, IgE, or four other anti-cell surface antibodies, nor were the changes induced by binding mAb AA4 at 4 degrees C or in the absence of extracellular calcium. Although mAb AA4 does not stimulate histamine release, it enhances the effect of the calcium ionophore A23187 mediated release. The morphological and biochemical effects produced by mAb AA4 are similar to those seen following activation of the cell through the IgE receptor. Therefore, the surface gangliosides which bind mAb AA4 may function in modulating secretory events.

Actins↗

PubMed1992

Ontogeny of prolyl endopeptidase, pyroglutamyl peptidase I, TRH, and its metabolites in rat pancreas.

We demonstrate that two enzymes, soluble unspecific pyroglutamyl peptidase I and prolyl endopeptidase, able to degrade thyrotropin-releasing hormone (TRH) in vitro were present in pancreas at the early stage of rat development. Specific particulate pyroglutamyl peptidase II remained undetectable during ontogenesis. Pyroglutamyl peptidase I specific activity increased until day 3 and decreased after day 5. Furthermore, prolyl endopeptidase specific activity rose slightly to a peak on postnatal day 20. A good correlation between immunoreactive TRH and deaminated TRH (TRH-OH) was found in the 1st wk after birth. However, His-Pro diketopiperazine (DKP) levels were stable and low during development. We show that hot acidic extraction conditions could artefactually generate His-Pro DKP. In vivo, active site-directed inhibitors of pyroglutamyl peptidase I and prolyl endopeptidase enzymes do not show any TRH-deamidating and/or pyroglutamyl peptidase I pathways in neonatal rat pancreas. The data suggest that these two enzymes are not involved in intra- or extracellular control of TRH levels in neonatal rat pancreas and that pancreatic TRH content appears to be principally regulated by biosynthetic steps. Nevertheless, low levels of endogenous His-Pro DKP and TRH-OH identified in neonatal rat pancreas suggest that TRH or TRH-like peptides may be metabolized in this tissue in intact rats, albeit at low rates.

Aging↗