Abstract
Abstract. Rat 

Abstract. Rat pituitary cells were dispersed with trypsin and separated by sedimentation at unit gravity. The distributions of prolactin (Prl) , luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were determined, and two enriched cell populations (mammotrophs and gonadotrophs) were subsequently cultured. During a 4 h incubation, gonadotrophin-releasing hormone (GnRH) stimulated the release of LH and of FSH by both the unfractionated population and the enriched gonadotrophs; the magnitude of this stimulation increased with the length of the pre-culture periods, and the amount of LH released into the medium correlated strongly with the amount of FSH, whatever the length of the pre-culture period. The cellular cAMP content was also enhanced during the 4 h incubation, but no correlation was found between the hormone release and the cAMP accumulation. Furthermore, during the first 30 min of incubation with GnRH there was no increase of cellular cAMP, whatever cell population used. We conclude that the gonadotrophin release was independent of the cAMP accumulation observed in pituitary cells several hours after stimulation by GnRH; conse- quently, the late increase in the nucleotide is suggested to be a non-specific secondary process.
Since early reports that cyclic adenosine monophosphate (cAMP) (GnRH) or by some of its analogues (Borgeat et al. 1972 (Borgeat et al. , 1974 Kaneko et al. 1973; Lippman 1975) ; furthermore, GnRH has been shown to stimulate the activity of adenylate cyclase in the pituitary (Makino 1973) , and cAMP derivatives have been reported to induce the release of gona¬ dotrophin (Ratner 1970; Jutisz & de la Llosa 1970) , or, more precisely, the first step ('sensitivity re¬ sponse') of the release (Kercret et al. 1977 (Duval et al. 1980 ).
Materials and Methods
Male Wistar rats 38 to 44 days old (C.E.R.J., Le Genest) were used. Synthetic GnRH was purchased from Interchim (Montluçon).
Cell dispersion
The cell suspension was prepared essentially as described by Hymer et al. (1973) (Snedecor 8c Cochran 1971) .
Results
As shown in Fig. 1A The basal release of both the gonadotrophins was very high immediately after cell dispersion and decreased with increasing pre-culture time (Table 1 ). The data show that there was more cAMP in the 'GONA' population than in the 'Prl' population.
However long the pre-culture period, GnRH stimulated the release of LH and FSH from the unfractionated cells ( Fig. 2A) (Fig. 3) , whereas the LH release and the increase in cAMP content were not.
The hypothalamic releasing hormone promoted the release of both gonadotrophins by the cells in the 'GONA' population (Fig. 2B) . The promoted LH and FSH releases were still highly correlated (r = 0.957, Fig. 4 ). The increase in cAMP content became significant after the 3rd day of pre-culture, but still no correlation with the release of gonado¬ trophin was observed (Fig. 4) 
AcAMP
Correlation between ALH and AFSH and between ALH and AcAMP for each assay pair from the 'GONA' population.
Two pre-culture times were used and are distinguished on the figure (0-o, 

{'paper_id': '26654042', 'title': 'Gonadotrophin release by gonadotrophs incubated with gonadotrophin-releasing hormone is independent of intracellular cAMP accumulation', 's2_url': 'https://api.semanticscholar.org/CorpusID:26654042', 'source': 'S2ORC'}