Pancreatic acinar cell function and morphology in rats fed zinc-deficient and marginal zinc-deficient diets.

The prevalence of marginal zinc nutriture in several populations of people in this country and the lack of reports on the effect of marginal zinc nutriture in experimental animals prompted us to look at pancreatic acinar cell function and morphology in rats fed a zinc-deficient diet ad libitum: 4 and 50 ppm zinc-supplemented diets in amounts isocaloric to a zinc-deficient diet and Rodent-Blox fed ad libitum for a period of 49 +/- 1 (SEM) days. Because of a diminished rate of energy expenditure in zinc-deficient rats, animals receiving 50 ppm zinc-supplemented diets were offered less food, resulting in decreased body weight and pancreas weight, DNA, RNA, total protein, lipase, amylase, and secretion of protein. Specific changes due to zinc deficiency included (a) further decrease in body weight and (b) increase in content, specific activity, and secretion of lipase. Both the size and volume fraction of zymogen granules were reduced in zinc deficiency. The lumina of acinar and small ducts were collapsed with paucity of secretion products. Zinc deficiency may therefore lead to a defect in discharge mechanism. A further reduction in volume fraction of zymogen granules in the 4 ppm zinc-supplemented group was associated with increased secretion of serine proteases (trypsinogen and chymotrypsinogen), which constitute approximately 46% of total secretory protein in the pancreas under normal dietary conditions. This indicated an accelerated discharge due to an unknown mechanism. Changes in the secretion of digestive enzymes in the present study simulated ethanol-induced secretory alterations that were previously observed. Because abnormal zinc nutriture and chronic alcoholism are commonly associated, it is speculated that zinc deficiency may play a role in the ethanol-induced secretory alterations.