Lysosomal Enzymes in the Rat Harderian Gland Are Altered by Either Bromocriptine Treatment or Hypophysectomy and Hormone Replacement Therapy

Four groups of adult male hypophysectomized rats were injected subcutaneously twice daily between 0800–0900 hr and 1600–1700 hr with either saline diluent, 150 μg sheep prolactin and/or growth hormone (GH); intact rats received either saline or 150 μg bromocriptine twice daily. After 4 days of treatment, lysosomal enzyme assays revealed significant elevations in both acid phosphatase and α-mannosidase enzyme activities in the Harderian glands of saline-injected hypophysectomized rats compared to those in intact controls. β-Glucuronidase levels were depressed and hexosaminidase activity unaffected by hypophysectomy treatment alone compared to intact controls. Lysosomal enzyme activities in hypophysectomized animals treated with prolactin were not different from the hypophysectomized control animals. However, treatment with GH alone or in combination with prolactin had a significant inhibitory effect on β-glucuronidase, hexosaminidase, and α-mannosidase enzyme activities in the Harderian gland of hypophysectomized animals. Bromocriptine treatment in intact rats only elevated acid phosphatase activity. In summary, the patterns of responses did not reveal a role for prolactin in the control of Harderian gland lysosomal enzyme activities by the pituitary. However, some of the influence on this target system may be exerted by growth hormone.