Three interrelated experiments were initiated to study growth hormone's stimulation of urinary sodium retention. First a dose-response curve was determined by administration of known dosages of growth hormone or the vehicle to groups of rats. Urine was collected from four to six hours after administration. In a second experiment, the relationship between time and degree of response to growth hormone was determined. Urine was collected from 0-2, 2-4, 4-6, 6-8, 8-10, 12-14, 16-18, and 20-22 hours after administration. Sodium excretion was not altered in the 0-2 hour collection period. Significant retention took place in both the 2-4 and 4-6 hour collection periods. The 6-8 and the 8-10 hour collections showed a gradual return to normal levels of sodium excretion. The 12-14 hour collection showed a significant increase in sodium excretion while the 16-18 and 20-22 hour collections returned to normal levels. The RNA inhibitor actinomycin D was used to determine if de nova synthesis of RNA might be involved in growth hormone's mechanism of sodium retention. Actinomycin D was given one-half hour before growth hormone. Urine was collected from four to six hours after administration. Actinomycin D alone did not alter sodium excretion and when administered with growth hormone, it blocked the antinatriuretic action. The relationship between the dose of growth hormone and the antinatriuretic response was found to be linear. Both the delay of antinatriuresis and the inhibition of this action by actinomycin D suggest that the antinatriuretic action of growth hormone is mediated via RNA synthesis.
Iowa Science Teachers' Journal
© Copyright 1969 by the Iowa Academy of Science
Bach, Ronald R.
"Nature of the Antinatriuretic Action of Growth Hormone,"
Iowa Science Teachers Journal: Vol. 6
, Article 11.
Available at: https://scholarworks.uni.edu/istj/vol6/iss4/11