Multiple species of follicle-stimulating hormone exist within the anterior pituitary gland of male golden hamsters

Abstract

Anterior pituitary glands were collected from immature and mature (intact and castrated) male hamsters. The various species of FSH present within these glands were separated by Concanavalin A (Con A) chromatography and polyacrylamide gel isoelectric focusing (PAG-IEF) and measured by a specific FSH radioimmunoassay (RIA) as well as a radioreceptor assay (RIA). Two distinct forms of FSH (Con A unbound and bound) were separated by Con A chromatography and detected by both RIA and RRA. These two populations of FSH were present within anterior pituitary glands of all three animal models tested. Castration before collection of anterior pituitary glands reduced the ratio of Con A unbound: bound immunoreactive FSH. When measured by RRA this reduction was no observed. When homogenates of anterior pituitary glands obtained from mature animals were separated by PAG-IEF, six distinct species of FSH were observed by RIA with isoelectric points (pI) of 6.0, 5.7, 5.3, 5.0, 4.7 and 4.2-3.8. Homogenates of anterior pituitary glands obtained from immature male hamsters did not contain one of these species of FSH (pI values 4.7). The relative contribution of some of the species of FSH to the total amount of detectable FSH differed depending upon the endocrine status of the animal. The species with pI value of 4.2-3.8 did not show any receptor-binding activity in any of the three models studied. The overall ratio of the activity of FSH measured by RRA compared with RIA was highest in anterior pituitary glands from intact mature and immature hamsters and lowest in anterior pituitary glands obtained from castrated animals. The RRA:RIA ratio for each species of FSH in all models tested declined as the isoelectric point of that species decreased. Thus, these results demonstrated the presence of multiple species of FSH within the anterior pituitary of immature and mature male hamsters. The relative proportions and receptor-binding activities of these species differed according to the isoelectric point and the pattern of hormone secretion at the time of collection of pituitary glands. Gonadal and other endocrine factors may influence not only the relative amount of each species of FSH but also the receptor-binding capacity of the FSH species synthesized by the anterior pituitary gland.

Microheterogeneity of pituitary follicle-stimulating hormone in male rats: differential effects of the chronic androgen deprivation induced by castration or androgen blockade

“…Although the effects of castration and steroid substitution have been extensively studied in hamsters Ulloa-Aguirre & Chappel, 1982) and female rats (Ulloa-Aguirre et al 1988ft, 1990, only a few studies have dealt with male rats, producing figure 2. Recovery of FSH bioactivity (as a percentage of total recov¬ ered) in various pH ranges after isoelectric focusing of pituitary homogenates from four groups of male rats under different conditions of androgen deprivation.…”

Immunological and Biological Activities of Pituitary FSH Isoforms in Prepubertal Male Rats: Effect of Antiandrogens

“…This differential glvcosylation, in turn, exerts a marked influence on circulating half-life, receptor binding affinity, and in vitro and in vivo biological activities [5], It has been shown that carbo hydrates are needed for the full expression of the biologi cal activity [6]. Sialic acid determines the circulating halflife of the hormone [7], as well as the receptor affinity in vitro [5], The results obtained in experimental animals as well as in studies carried out in children, adults, and aging men and women under different physiological conditions have shown that the hormonal status regulates the sialic acid content of FSH isoforms [8,9], In males, differences have been demonstrated in charge distribution by castra tion [10,11], antiandrogen administration [12], during sexual maturation [13,14], and by in vitro testosterone treatment [15]. There is no evidence of the hormonal influence upon the carbohydrate inner structure of pitu itary FSH isohormones and the relationship between this carbohydrate inner structure of FSH isohormones and their bioactivity.…”

Effects of 17β-Estradiol on Distribution of Pituitary Isoforms of Luteinizing Hormone and Follicle-Stimulating Hormone during the Follicular Phase of the Bovine Estrous Cycle1

“…Generally in most species, the most basic LH isoforms have the greatest bioactivity, whereas the more acidic LH isoforms have lower bioactivity [4,8,9,13,14], with the exception of the ovine and bovine species, in which the mid-alkaline LH isoform of F has greater bioactivity than either the more alkaline or acidic LH isoforms [5,12]. Similarly, receptor binding activity of the hamster [15] and rat [16] FSH isoforms declines as the pI decreases. However, more acidic rat FSH isoforms display a longer circulatory half-life in vivo [17].…”

“…Distribution of the isoforms in the pituitary varies during stage of the reproductive cycle in rodents [18][19][20] and primates [21], and differs as a result of castration in rodents [3,9,14,15], sheep [5], and cattle [12] or as a result of steroid hormone replacement in sheep [5] and cattle [12]. Interestingly, the amounts of biologically potent basic isoforms of LH increase during the preovulatory surge of gonadotropins in the rat [18] and during the midcycle surge of gonadotropins in primates [21,22], whereas the amounts of biologically less potent, more alkaline or acidic rat LH isoforms remain constant throughout the entire estrous cycle [18].…”