A Comparison of Bioactivity and Immunoactivity of Luteinizing Hormone Stored in and Released inVitrofrom Pituitary Glands of Rats under Various Gonadal States*

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Abstract
LH released in vitro upon stimulation with LHRH was compared with LH remaining in the gland, using pituitaries taken from intact male rats, spayed female rats, and spayed rats that had been treated with estrogen. With intact and spayed, treated rats, but not with spayed ones, the released LH had a significantly higher biological to immunological activity (B:I) ratio than did that extracted from the glands, regardless of whether a radioreceptor or a testosterone production assay was used for bioassay. However, B:I ratios of LH released from all three types of glands under basal conditions were indistinguishable from each other and from those of tissue LH. The observed B:I ratio differences were not attributable to contamination with gonadotropin subunits but rather seem to be due to differences in LH itself. The B:I ratio differences remained the same throughout 6 h of incubation, during which the quantity of LH in medium increased linearly from 1-6 h. Comparisons of the two kinds of LH revealed no differences in apparent molecular size or plasma survival time. These results suggest that 1) the B:I ratio of LH released in vitro in response to LHRH can be influenced by gonadal steroids, and 2) the gonadal steroids have no measurable effect on the B:I ratio of LH stored in the gland or that of LH released in vitro in the absence of LHRH.