Hepatomegaly induced by the pulsatile, but not continuous, intravenous administration of purified chicken growth hormone in broiler pullets: liver composition and nucleic-acid content.

The present study determined the composition and nucleic-acid content of livers obtained from 11-wk-old, broiler-strain pullets infused with pituitary-derived chicken growth hormone (p-cGH) in either a pulsatile (Study 1) or continuous (Study 2) manner for 21 days. Pulsatile p-cGH administration resulted in a decrease in ratios for liver DNA to wet weight (P less than .01), DNA to protein (P less than .03), and DNA to RNA (P less than .002), compared with controls. Total RNA-to-liver ratio (P less than .003) and liver weight (P less than .007) were significantly elevated, compared with controls. Total grams of protein (P less than .0007), water (P less than .004), and ash (P less than .01) were also elevated, with no significant differences in the percentage of composition. Continuous growth-hormone (GH) administration resulted in a decrease in the DNA-to-protein ratio (P less than .04) and a modest increase in the mass of liver protein (P less than .11) in comparison with controls, suggestive of cell hypertrophy. On a mass and percentage basis, liver composition was otherwise unaffected by the continuous administration of GH. In summary, pulsatile administration of GH induced hepatomegaly, largely due to cell hypertrophy, with no change in relative tissue composition. The continuous administration of GH had no effect on liver size, tissue composition, or most nucleic-acid-based indicators of cell hypertrophy or hyperplasia. Thus, previously observed differences in overall growth performance due to pattern of GH administration were also reflected in selected target-tissue response.