Long-term effects of neonatal hormonal treatments on plasma prolactin levels in female BALB/cfC3H and BALB/c mice.

In view of morphological indications that the effect of neonatal sex steroid exposure on mammary gland devel opment and tumorigenesis in mice may be a consequence of sustained prolactin secretion, homologous radioimmunoassay was used to measure plasma prolactin levels in variously treated mice at several ages. Female BALB/cfC3H/Crgl and BALB/cCrgl mice received daily s.c. injec tions of 5 /,g diethylstilbestrol, 20 /¡gdiethylstilbestrol, 20 /<g 17/3-estradiol, 20 /jg testosterone, or 20 /.<g ovine prolactin for the first 5 days of postnatal life. In mice killed at about 2, 7, and 15 months of age, plasma prolactin levels of BALB/cfC3H females treated neonatally with diethylstilbestrol, 17/3-estradiol, or prolactin were compa rable with those of the controls at proestrus/estrus and usually were significantly higher than the levels in those at metestrus/diestrus. Prolactin levels in mice treated with testosterone were usually significantly higher than were those in the other treated groups and in all control groups. In BALB/c females at about 7 and 15 months, most steroid-treated groups showed prolactin levels greater than control values at metestrus/diestrus but comparable with those at proestrus/estrus. However, tes tosterone treatment resulted in levels greater than those of controls at either stage. In both substrains mice given steroid hormones or diethylstilbestrol lacked ovarian cor pora lutea at all ages, but control mice and mice receiving prolactin showed corpora lutea. Mammary gland re sponses to neonatal steroid or diethylstilbestrol treatment may in part be ascribed to continuous estrogen stimula tion of prolactin secretion.