The effect of chronic apomorphine treatment on the ultrastructure of the prolactin cells and on plasma prolactin levels in young and aged male Wistar rats.
Effects of two doses of apomorphine on the plasma prolactin (PRL) levels and on the ultrastructure of PRL cells in young and aged male Wistar rats were investigated. In young and aged control rats no significant differences were found between the plasma PRL levels. Immunocytochemical staining with anti-r-PRL revealed significant differences between young and aged control rats; in young rats the number of PRL cells with polymorphic granules exceeded the number of cells with round granules, whereas in aged rats almost exclusively cells with round granules were found. In young rats, chronic treatment with a low dose (0.01 mg/kg/day) of apomorphine did not result in a significant change in plasma PRL level or cell morphology. However, high dose (0.25 mg/kg/day) of apomorphine resulted in a significant decrease in plasma PRL levels, a decrease of number of cells with polymorphic granules and an increase of cells with round granules. The occurrence of PRL cells with round granules and plasma levels was negatively correlated. In aged rats, apomorphine (0.01 or 0.25 mg/kg/day) treatment did not affect plasma levels nor did it affect the distribution of the cell types. We conclude that in young rats PRL cells are sensitive to apomorphine and that their ultrastructure reflects a phase of the secretory cycle. In aged rats, the cells appear to have lost their sensitivity to apomorphine. The fact, that the distribution over the different cell types in control aged rats is similar to that of the apomorphine-treated young rats, suggests a strong influence of endogenous dopamine on PRL cell physiology in the aged rat.
van Putten
L J
LJ
Department of Anatomy and Embryology, Faculty of Medicine and Dentistry, University of Nijmegen, The Netherlands.
de Rijk
E P
EP
Flik
G
G
D000818:Animals; D001058:Apomorphine / Q000493:pharmacokinetics*; D001773:Blood Cells / Q000187:drug effects* / Q000648:ultrastructure; D008297:Male; D011388:Prolactin / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains
D011388:Prolactin; D001058:Apomorphine