S. Valenti et al., IMMUNOREACTIVE AND BIOACTIVE LH-RELEASE FROM PITUITARIES OF INTACT ORCASTRATED MALE-RATS - EFFECT OF IN-VITRO GNRH AND KCL ADMINISTRATION, Journal of endocrinological investigation, 20(7), 1997, pp. 381-386
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.