Growth hormone (GH) receptor and GH-binding protein deficiency in the growth failure of potassium-depleted rats.

Potassium (K+) deficiency is associated with growth retardation in both man and experimental animals. Growth hormone (GH) administration to such animals prevents, to some extent, weight loss and selective muscle atrophy, but does not affect tail and tibia length even with supraphysiological doses. The present study was undertaken to investigate the possible effect of K+ deficiency on the hepatic GH receptor and GH-binding protein (BP). Young female Wistar rats were maintained on K(+)-deficient fodder and distilled water, and compared with pair-fed and ad-libitum-fed control groups. After 15 days GH-BP and electrolytes were measured in sera, GH receptors were studied in liver membranes by 125I-labeled human GH binding and muscles were weighed and saved for electrolyte measurements. K(+)-deficient rats showed complete growth arrest compared with an intermediate weight gain of the pair-fed group. Serum K+ was very low, at 1.5 +/- 0.1 mmol/l, compared with the mean value of 5.3 mmol/l of control animals. Somatogenic and lactogenic receptors in liver membranes and serum GH-BP levels were significantly (P < 0.05) lower in K+ deficiency, as compared with their pair-fed controls. Liver GH receptors correlated significantly (P < 0.05) with serum GH-BP levels. The growth variables correlated positively with both hepatic somatogenic and lactogenic receptors and serum GH-BP levels, with correlation coefficients that were highest against serum GH-BP and lowest against liver lactogenic receptors. Serum and muscle K+ correlated significantly (P < 0.05) with both liver GH receptors and serum GH-BP, with correlation coefficients that were higher against serum GH-BP.(ABSTRACT TRUNCATED AT 250 WORDS)