In VivoEffects of Antisera to Prolactin Receptors in Female Rats*

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Abstract
Antisera generated in guinea pigs against partially purified PRL [prolactin] receptors derived from rabbit mammary glands were tested for their effect on PRL binding and the biological effects of PRL in vitro and in vivo. Several dilutions of either normal guinea pig serum or anti-PRL receptor serum were incubated in vitro with homogenates of rat ovaries. Although specific binding of PRL was inhibited as much as 90% by the antiserum, normal guinea pig serum had little effect. There was no inhibition of binding of LH [luteinizing hormone] and FSH [follicle stimulating hormone] to ovaries by these antisera. When these antisera were administered to normal cycling rats, the most pronounced effect was an increase in the number of corpora lutea, presumably due to the prevention of the luteolytic effect of PRL. When 1 of these antisera was given to adult rats immediately after parturition, weight gain of their pups decreased significantly, possibly reflecting a decrease of milk yield. Passive immunization of animals with anti-PRL receptor sera modifies the actions of PRL on some of its target tissues.