Acute and Subacute Effect of LH-RH upon LH-and FSH-Gonadotrophs in Castrated Female Rats with Short-Term Estrogen-Progesterone Pretreatment

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Acute effect of synthetic LH-RH upon LH and FSH-gonadotrophs in prepuberally ovariectomized female rats 3days after a short-term estrogen-progesterone treatment was investigated electron microscopically along with the radioimmunoassay of LH and FSH. Thirty days after ovariectomy, so-called central LH-gonadotrophs dispersed, but the castration cells which might originate from FSH-gonadotrophs accumulated in the central area of the gland; most of peripheral LH-gonadotrophs became slightly affected, although there was a possibility that some of them took an appearance of castration cells. Secretory granules were considerably driven out of castration cells filled with dilated cisternae. Following the estrrgen-progesterone pretreatment, some peripheral castration cells quickly dispersed and normal ovoid LH-gonadotrophs filled with secretory granules appeared again. Central castration cells were not, however, recovered from their cell hypertrophy, but from the reduction in size of cisternae. Steroid pretreatment thus could enough prevent the release of granules from the castration cells. Those rats were i. v. injected with LH-RH 100ng/m<I>l</I>/rat 33 days after the castration. Serum LH was highest after 5 and 10min, but mean pituitary LH content was unchanged through the testing periods except for diminution at 5 and 180min. Serum FSH concentration rose slightly, but mean pituitary FSH content showed no change except for diminution at 5 and 180min. Morphologically, LH-RH temporally and slightly deprived peripheral LH-cells of the secretory granules within 5min and made central LHcells visible again within 5 and 10 min through their granulation. On the other hand, LH-RH exerted the primary effect upon FSH-castration cells to drive out transiently but efficaciously the secretory granules within 5, 10min or later, along with the more profound contraction of cisternae. The interval of 5min may be assumed as the “discharging phase” of LH-gonadotrophs, and the interval between 5 and 10min as “primary short-term discharging phase” of FSH-gonadotrophs. Subsequently, both kinds of gonadotrophs began to reproduce their secretory granules. The interval between 10 and 30min may be called “synthesizing phase” of FSH-gonadotrophs; the interval up to 60 min may represent the “storage phase” taking the form of FSH-castration cells. LH-RH exerted the secondary, mild but prolonged effect of granular discharge upon FSH-castration cells within 180min causing a transformation into the typical castration cell with numerous open cisternae. Signet-ring cells were, however, scarcelly changed in response to this dose of releasing hormone. It was concluded that LH-RH would act not only slightly upon LH-gonadotrophs but also biphasically upon FSH-gonadotrophs to discharge the secretory granules which may be associated with LH secretion both in acute and subacute periods. Evidences for the intrinsic capacity of so-called FSH-gonadotrophs to secrete LH in contradiction to their name are now available. It is therefore quite hard to identify certainly LH-gonadotroph with FSH-gonadotroph on the basis of their morphological criteria.
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Acute and Subacute Effect of LH-RH upon LH-and FSH-Gonadotrophs in Castrated Female Rats with Short-Term Estrogen-Progesterone Pretreatment

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