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Sexually Dimorphic Interaction of Insulin‐Like Growth Factor (IGF)‐1 and Sex Steriods in Lactotrophs
Author(s) -
Chowen Julie A.,
GonzálezParra Silvia,
GarcíaSegura Luis Miguel,
Argente Jesús
Publication year - 1998
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1998.00228.x
Subject(s) - medicine , endocrinology , prolactin , dihydrotestosterone , prolactin cell , testosterone (patch) , biology , somatostatin , somatotropic cell , hormone , insulin like growth factor , sexual dimorphism , growth factor , androgen , pituitary gland , receptor
Anterior pituitary hormone secretion is sexually dimorphic due partially to gender differences in the postpubertal hormone environment; however, differences in the pituitary’s responsiveness to these signals may also play a role. We have used simple and double in situ hybridization to determine whether lactotrophs and somatotrophs from male and female rats respond differently in vitro to growth hormone‐releasing hormone (GHRH), somatostatin (SS) or insulin‐like growth factor (IGF)‐I and whether sex steroids modulate these responses. Cultures were treated with either 17 β ‐estradiol (E; 10 −9 M ), testosterone (T; 10 −7 M), dihydrotestosterone (DHT; 10 −7 M) or vehicle in combination with either GHRH (10 −7 M), SS (10 −7 M), IGF‐I (10 −7 M) or vehicle. Basal mRNA levels of GH, prolactin (PRL) and pituitary transcription factor‐1 (Pit‐1) did not differ between the sexes. The responses to peptide hormones alone were similar between the sexes, but not in the presence of gonadal steroids. In females, DHT reduced and E increased the stimulatory effect of GHRH and inhibitory effect of SS on GH mRNA levels (two‐way ANOVA : P<0.05), while having no effect in males. An additive effect of E and GHRH on PRL mRNA levels was seen only in males. The E induced rise in PRL mRNA levels was completely inhibited by SS in females, but only partially so in males (two‐way ANOVA : P<0.001). IGF‐I inhibited the E induced rise in PRL and lactotroph Pit‐1 mRNA levels only in females. These results suggest that sex steroids modulate the pituitary’s response to hypothalamic and circulating factors differently in males and females and that this may play a role in generating the sexually dimorphic patterns of pituitary hormone secretion.