THE EFFECTS OF BROMOCRIPTINE AND PROLACTIN ON PORPHYRIN BIOSYNTHESIS IN THE HARDERIAN-GLAND OF THE MALE HAMSTER, MESOCRITECUS-AURATUS

Porphyrin biosynthesis was examined in the Harderian gland of the male golden hamster by fluorometric assays of gland porphyrin content and by measuring the activity of a rate-limiting enzyme for haem biosynthe sis, 5-aminolaevulinic acid synthase. Both porphyrin content and enzym e activity are low in normal male glands but were greatly raised in ma les castrated for 6 weeks. However, porphyrin synthesis remained at ba sal levels in castrates given the dopamine agonist bromocriptine; this suppression could be reversed by simultaneous prolactin administratio n, and castrated males receiving prolactin alone exhibited very high e nzyme activity and porphyrin content. Bromocriptine also prevents the morphological feminisation of the Harderian gland which would normally occur after castration; again, the simultaneous administration of pro lactin permits feminisation to occur. The results support the hypothes is that, while androgens have an inhibitory effect on porphyrin synthe sis within this model, other factors, including prolactin, are permiss ive.