QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lee, S. C. Articles by Harper, A. E. Search for Related Content PubMed PubMed Citation Articles by Lee, S. C. Articles by Harper, A. E.

Rat Liver Histidase: Glucose Repression and Half-life after Casein Hydrolysate Feeding¹

The Departments of Nutritional Sciences and Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706

Histidase, the first enzyme in the major catabolic pathway of histidine, increases in animals fed a large quantity of amino acids but the induction is suppressed if glucose is fed with the amino acids. This investigation was undertaken to determine whether glucose suppression would be influenced by glucagon or cyclic adenosinemonophosphate (c-AMP). Hepatic histidase activity of protein-depleted rats increased twofold within 16 hours after they were force-fed casein hydrolysate, but the increase was prevented if they were force-fed glucose at the same time. Administration of glucagon or dibutyryl cyclic AMP to protein-depleted rats also increased histidase activity, and administration of either of these substances counteracted the glucose repression. The hepatic histidase activity was elevated in alloxan-diabetic rats but decreased significantly when the diabetic animals were treated with insulin. The concentration of liver cyclic AMP increased in rats force-fed casein hydrolysate but not when glucose and casein hydrolysate were fed together. These results suggest that cyclic AMP is involved in the induction of histidase by casein hydrolysate and suppression of this response by force-feeding glucose. The apparent half-life of hepatic histidase in protein-depleted rats force-fed casein hydrolysate was 2.1 days, comparable to the value obtained from measurements on rats fed ad libitum an 80% casein diet for 14 days. Total liver histidase activity was maintained in rats starved for 5 days although total liver protein decreased.

KEY WORDS: • casein hydrolysate • glucose • cyclic AMP • histidase

¹ Supported by funds from the College of Agricultural and Life Sciences, University of Wisconsin; U. S. Public Health Service Grant AM 10748 from the National Institute of Arthritis and Metabolic Diseases; and by Public Health Service International Post-doctoral Research Fellowship no. 5 F05 TW01480-02, IFRC.

² National Institutes of Health International Post-doctoral Fellow. Present address: Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, China.

Manuscript received 5 August 1971.