Glycosylated growth hormone: detection in murine pituitary gland and evidence of physiological fluctuations.

We examined murine pituitary glands for glycosylated growth hormone using a lectin-binding immunoassay. Every gland tested exhibited significant concanavalin A-binding growth hormone immunoreactivity. The activity was lower in female rats than in males, and lower in lactating than in virgin females. The activity increased following ovariectomy, although total immunoreactive growth hormone was not altered. Administration of estradiol benzoate decreased the concentrations of both types of growth hormone. Progesterone administration, in contrast, did not change concanavalin A-binding growth hormone, but it lowered total growth hormone. Western blotting revealed a growth hormone immunoreactive band 4-5K heavier than the growth hormone monomer in both rat and mouse pituitary. These data suggest the existence in the murine pituitary of a glycosylated form of growth hormone that undergoes physiological fluctuations.