Diethylstilbesterol- and pregnancy-induced changes in rat neurointermediate lobe oxytocin, arginine vasopressin, methionine enkephalin and dynorphin.
The neurointermediate lobe of the pituitary (NIL) contains the opioid peptides methionine enkephalin (MENK) and dynorphin 1-8 (DYN) in addition to oxytocin (OT) and vasopressin (AVP). If the opioids have a functional role, such as feedback control on OT or AVP release, the content or release of the opioids might be expected to change under conditions in which OT or AVP change. This expectation was examined by studying the synthesis, storage and release of the 4 peptides under conditions in which OT and AVP dynamics are known to be altered. Diestrus, diethylstilbesterol(DES)-treated, and day 22 pregnant rats were decapitated, the hypothalamo-neurohypophysial system (HNS) excised and either superfused in oxygenated Krebs buffer at 37 degrees C or stored at -80 degrees C for measurement of paraventricular and supraoptic nuclei mRNA content by in situ hybridization analysis. Peptide content of superfusates and NIL homogenates were determined by specific RIAs. Compared with diestrus animals, DES treatment increased NIL OT but decreased MENK. In term pregnant rats, NIL OT, AVP, and DYN were increased over diestrus values, while MENK was again decreased. Release of the peptides from the isolated HNS paralleled changes in NIL content. The hypothalamic mRNA for OT was increased in DES-treated and pregnant rats while MENK mRNA was decreased. AVP and DYN mRNA was increased in pregnant animals. Although the NIL was found to contain much more immunoreactive OT and AVP than MENK or DYN, under basal conditions the release of MENK was equal to or greater than the release of OT, while the release of DYN approached that of AVP.(ABSTRACT TRUNCATED AT 250 WORDS)
Schriefer
J A
JA
Department of Pharmacology, West Virginia School of Osteopathic Medicine, Lewisburg.
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D004054:Diethylstilbestrol / Q000494:pharmacology*; D004399:Dynorphins / Q000378:metabolism; D004723:Endorphins / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism; D005260:Female; D010121:Oxytocin / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism*; D010909:Pituitary Hormones, Posterior / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D004723:Endorphins; D010909:Pituitary Hormones, Posterior; D001127:Arginine Vasopressin; D010121:Oxytocin; D004744:Enkephalin, Methionine; D004054:Diethylstilbestrol; D004399:Dynorphins; D011188:Potassium