Effects of age and sex on basal and dopamine-inhibited in vitro prolactin release, and dopamine receptor binding, by the rat adenohypophysis.
We measured basal and dopamine-inhibited pituitary cell prolactin (PRL) release in vitro, and dopamine receptor binding in pituitary homogenates, from intact male and female Wistar rats of varying ages. During 48-72 hours in culture, the baseline secretion rate of PRL from pituitary cells of old (24 months) male rats was less than one-half that from cells of mature (6 months) male rats, whereas the corresponding basal secretion rate of PRL from cells of old female rats was nearly 3-fold greater than that from cells of mature female rats (p < 0.001). After in vitro exposure to various concentrations of dopamine (10(-10)M to 10(-6)M), PRL secretion decreased from pituitary cells of both mature and old rats (p < 0.001). However, repeated measures analysis of variance revealed an age-related dose-dependent decrease in the magnitude of dopamine-inhibited PRL release from cells of both male and female rats (p < 0.001). Dopamine receptor number did not differ with age (3-25 months), but was 2 to 3-fold greater in female than in male rats (p < 0.01). Receptor affinity was decreased with age only in female rats, and was greater in female than in male rats (p < 0.05). These data suggest that the decrease in dopamine-inhibited PRL release from pituitary cells of old male and female rats is not due to altered pituitary dopamine receptor binding, despite certain sex differences.
Kochman
K
K
Molecular Physiology and Genetics Section, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224.
Kowatch
M A
MA
Roth
G S
GS
Blackman
M R
MR
D000367:Age Factors; D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D008297:Male; D010903:Pituitary Gland, Anterior / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011954:Receptors, Dopamine / Q000032:analysis* / Q000378:metabolism; D012737:Sex Factors; D013134:Spiperone / Q000378:metabolism
D011954:Receptors, Dopamine; D013134:Spiperone; D011388:Prolactin; D004298:Dopamine