Effects of desiccated thyroid, propylthiouracil, vitamin B 12 and caloric restriction on somatic growth, food intake and dentinogenesis in cortisone-treated immature albino rats

Abstract

Seven groups of twenty male rats were weaned and given an intraperitoneal injection of alizarin red S at 21 days of age. For the next 20 days the rats were reared on one of the following dietary regimes: 1, CAdeit (0d2 mg cortisone/g food) ad libitum; 2, TCAdiet (0.2 mg desiccated thyroid/g CAdiet) ad libitum; 3, PTUCAdiet (0.2 mg propylthiovracil/g CAdiet) ad libitum; 4, Rdiet (control food) ad libitum; 5, Rdiet in restricted amounts; 6, B 12CAdiet (200 μg vitamin B 12/kg CAdiet ad libitum; 7, B 12CAdiet in restricted amounts. The 21–41 day increments of dentine were measured on tracings of comparable, central, undecalcified sections (95–105μthick), cut mesio-distally, parallel to the long axes of the mandibular first molars. Body weight and food intake of the 140 rats were recorded regularly. The final wet weights of the adrenal glands, submaxillary together with the major sublingual salivary glands, testes and eyes were recorded for ten rats in each of the seven groups. Results showed that CAdiet retarded dentinogenesis and increments in body weight, depressed food intake and weights of all glands and organs. Caloric restriction also affected somatic growth, but markedly less than CAdiet. Dentine apposition was not retarded by the caloric restriction. TCAdiet resulted in greater food intake and body weight than did CAdiet. The desiccated thyroid did not alter the effects of cortisone on weights of glands and organs, but apparently augmented the depressing effects on dentine formation. Propylthiouracil produced goitre. The PTUCAdiet resulted in smaller food intake, i.e. cortisone-dosage, and did not per se augment the effects of cortisone on dentinogenesis, on body weight, on weights of organs and glands, except the adrenals which were markedly smaller than those of rats raised on the CAdiet. Vitamin B 12 resulted in greater food intake, i.e. cortisone-dosage, of rats raised on the B 12CAdiet ad libitum. B 12 did not protect the rats from the effects of cortisone on body weight, but did in part counteract the retardation of dentinogenesis and of salivary gland weight. Finally, exophthalmos occured in 80 per cent of all cortisone-treated rats, it was not due to enlarged eyes per se.