SUBCELLULAR-DISTRIBUTION OF PROTEIN-KINASE-C (PKC) IN ERYTHROCYTES AND CONCENTRATION OF D-MYO-INOSITOL-1,4,5-TRISPHOSPHATE (IP3) IN PLATELETS AND MONOCYTES OF FORCE-FED ZINC-DEFICIENT RATS

The purpose of the present study was to investigate whether alimentary zinc (Zn) deficiency affects the activities of the Zn metalloenzymes protein kinase C (pKC) and the phosphatidylinositol-specific phospholi pase C (PLC) in force-fed Zn-deficient rats. The in vivo activity of p KC was determined by measuring the subcellular distribution of the enz yme between the cytosolic and the particulate fraction of erythrocytes , whereas the activity of PLC was measured indirectly through the conc entration of its metabolite inositol-1,4,5-trisphosphate (IP3) in plat elets and monocytes. For this purpose, 24 male Sprague-Dawley rats wit h an average live mass of 126 g were divided into 2 groups of 12 anima ls each. The Zn-deficient and the control rats received a semisyntheti c casein diet with a Zn content of 1.2 and 24.1 ppm, respectively. All animals were fed the same amount of the diet (10.8 g dry matter [DM]/ d and rat) four times daily by gastric tube. After 12 d, the depleted rats were in a state of severe Zn deficiency, as demonstrated by a 70% lower Zn concentration and a 66% reduction in the serum activity of a lkaline phosphatase. The radioimmunologically determined concentration of IP3 was reduced by a significant 55% in the platelets of the Zn-de ficient rats (8.4 pmol IP3/5.10(8)) as compared with the control rats (18.8 pmol IP3/5.10(8)), whereas the IP3 concentration in the monocyte s was not affected by the alimentary Zn supply (1.4 vs 1.2 pmol IP3/10 (6)), nor was there any difference between the Zn-deficient and the co ntrol rats with regard to the radioenzymatically determined specific a ctivity of pKC, either in the cytosolic fraction (32.7 vs 32.5 pmol P/ min/mg protein) or in the particulate fraction (38.1 vs 36.5 pmol P/mi n/mg protein) of the erythrocytes.