Lack of somatotropin effect on glycosaminoglycan content of canine coronary arteries

Abstract

Eight beagles, 10 months of age, were surgically hypophysectomized and subsequently maintained without hormonal replacement therapy for 8 weeks. Four of the animals then received daily injections of bovine somatotropin (0.2 mg/kg subcutaneously for 3 weeks), while the remaining 4 were treated with saline. Six age-matched intact beagles served as normal controls. Following sacrifice, the aorta and both coronary arteries were dissected from each dog and analyzed for glycosaminoglycans (GAG, mucopolysaccharides). Four fractions were determined : hyaluronic acid (HA), heparan sulfate (HS), dermatan sulfate (DS), and the isomeric chondroitin sulfates (CS). In coronary arteries hypophysectomy had no effect on HA, but caused a significant reduction of HS, DS, and CS concentrations resulting in a marked lowering of the total GAG content. Treatment with somatotropin (GH) had no appreciable effect on any one of the four GAG constituents. The lack of sensitivity of coronary arteries to GH is contrary to the effectiveness of the hormone in raising sulfated GAG in aortas, which was previously demonstrated by us in hypophysectomized dogs and now confirmed again in the present series of experiments. The data support our hypothesis that there is a differential sensitivity to GH in the various parts of the vascular system.