Abstract
The rise in plasma free fatty acids (FFA) after parenteral administration of somatotropin preparations has been well-documented in several species tested with material from various sources(1–3). It is recognized that growth hormone preparations available are contaminated with small amounts of other pituitary principles; for brevity, the term somatotropin (or growth hormone) will be used in place of somatotropin preparation. This report concerns the response to an ovine (sheep) somatotropin in the guinea pig, a test animal heretofore not found responsive to several somatotropins (4).
Materials and methods. Male guinea pigs of mixed color, initial weight varying from 250–300 g, were used. Somatotropin used in these studies included ovine‡ and bovine§ growth hormones, each prepared by potassium chloride-cold ethanol fractional purification(5), and human growth hormone,∥ obtained by the acetic acid extraction procedure(6). Assay of the sheep and beef preparations for other pituitary hormones was performed by the supplier, and in each case contamination was negligible. Prior to testing, the animals were fed guinea pig chow¶ and water ad lib. At the twelfth hour of a 16-hour fast, each guinea pig received a 1 ml intraperitoneal injection of either a control solution, ovine growth hormone (5 mg), bovine growth hormone (5 mg) or human growth hormone (2 mg). The lower dose of human somatotropin was based upon studies (7) indicating that human growth hormone has a much smaller molecular weight than bovine somatotropin, and also the effective dose of the human preparation in the dog and in the rat is smaller than of the bovine material. The diluent for each somatotropin preparation was the control solution: distilled water with sufficient 0.1 N NaOH added to dissolve the dry powder, to a final concentration of 5 mg growth hormone per ml (bovine and ovine) or 2 mg per ml (human).
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