Upregulation of the L-type Calcium Channel in Renin-Positive Smooth Muscle Cells of Arterioles in the Kidneys of Rats with Streptozotocin-Induced Diabetes.

Objective: To estimate the number of L-type calcium (Ca2+) channels in the afferent and efferent arteriolar renin-positive and renin-negative smooth muscle cells and endothelial cells of the kidney arterioles in order to seek a relationship between the cell functions and the number of ion channels in the cell membranes.

Study design: In diabetes the main source of renin/prorenin is the tubules, while the renin granulation of the afferent arterioles is increased relative to the normal. The release of renin is related to the Ca2+ levels of the intracellular and extracellular spaces of the afferent arterioles. The L-type calcium channel blockers have a stimulatory effect on the renin system. The immunohistochemical signal of the antibody against the L-type Ca2+ channels was estimated stereologically.

Results: In the diabetic kidney the relative number of L-type Ca2+ channels on the surface of the renin-positive cells of the afferent arterioles was significantly increased. In the normal kidney there was a difference in the relative number of L-type Ca2+ channels on the surface of the endothelial cells between the renin-positive and renin-negative profiles of the afferent arterioles.

Conclusion: The increment in the number of Ca2+ channels on the renin-positive cell surface in the diabetic kidney could be related to the high renin granularity of the afferent arterioles. In the normal kidney the differences in the number of L-type Ca2+ channels on the endothelial cell surface may play a role in the higher permeability of the renin-positive part of the afferent arterioles.