IMMUNOREACTIVE AND BIOACTIVE LH-RELEASE FROM PITUITARIES OF INTACT ORCASTRATED MALE-RATS - EFFECT OF IN-VITRO GNRH AND KCL ADMINISTRATION

The in vitro immunoreactive (i-LH) and bioactive (b-LH) LH release fro m hemipituitaries of intact adult: male rats (INT) or rats castrated 7 days earlier (GAS) was studied. Hemipituitaries were incubated for 30 min (time 1) plus an additional 30 min (time 2) with GnRH (10 nM) and /or KCl (50 mM), according to one of the following protocols, media al one (C), KCl+KCl (K/K), GnRH+GnRH (G/G), KCl+GnRH (K/G), GnRH+KCl (G/K ). All of the hemipituitaries were further incubated in media alone fo r 120 min (time 3). i-LH, b-LH and i-FSH were assayed on the media. In both models, the highest bioactive:immunoactive (b/i) ratio was noted during time 1, however, CAS always secreted more b-LH than INT at any given time of the study. in INT, GnRH - but not KCl -administration d uring time 2 resulted in blunted i-LH. During the same time, the b/i r atios decreased in all groups but Gift. LH secretion recovered during time 3 in all groups, in GAS, i-LH levels comparable to those of time 1 were sustained by either stimulus during time 2, while the b/i ratio s were markedly decreased. LH secretion recovered in the K/K group dur ing time 3. These results suggest that: 1) promptly releasable pools o f b-LH are available in both models; 2) CAS always secrete more b-LH; 3) in INT, desensitization occurs involving parallel changes in both i -LH and b-LH, while changes in b-LH rather than i-LH are noted in GAS; 4) prolonged KCl administration might play a role in new gonadotropin synthesis and/or release. (C) 1997, Editrice Kurtis.