Abstract
Thyrotropin-releasing hormone was injected into the duodenum of two 500-kg steers, placed into the abomasum of two prepubertal bulls, and fed to four bull calves (1 to 3 wk of age) to test the effect on concentrations of prolactin and growth hormone in blood serum. Before 20 and 200mg of thyrotropin-releasing hormone were injected into the duodenum, prolactin in serum averaged 7.5 and 9.4ng/ml and increased to 52.5 and 129.6ng/ml at 45 and 35min after treatment. Average growth hormone concentration of serum was increased also, but the response was more variable than prolactin. Peak concentrations of prolactin and growth hormone in blood serum were 5 to 10 times greater after treatment with thyrotropin-releasing hormone (40 mg/100kg body weight into abormasum) than before treatment. Within 30min after oral administration of thyrotropin-releasing hormone (0, .5, 1, and 2mg/kg body weight) growth hormone concentration of serum was 30, 306, 356, and 317% greater than pretreatment. Prolactin concentration of serum, however, was increased in only one calf.
Published Version
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