DECREASED SKIN BLOOD-FLOW EARLY IN THE COURSE OF STREPTOZOTOCIN-INDUCED DIABETES-MELLITUS IN THE RAT

We have previously used laser Doppler technology to demonstrate that s kin blood flow is reduced in Type 1 (insulin-dependent) diabetic patie nts. The possibility of using the skin as an extremely accessible indi cator of diabetic microvascular disease is attractive. The streptozoto cin diabetic rat is an appealing potential animal model. We performed measurements of skin blood flow in two rat species, nine Sprague Dawle y (SD) rats and nine Wistar Kyoto (WKY) rats, observing early changes following the inception of diabetes. Four of the SD rats and five of t he WKY rats were made diabetic, the rest serving as controls. There we re no significant differences in skin blood flow between the two rat s trains. As in man, there appear to be rat skin sites with primarily nu tritive capillary supply and those with arteriovenous anastomotic pred ominance. The back and base of tail, both hair-covered areas, demonstr ated low flow characteristics, consistent with nutritive perfusion. In contrast, the plantar surface of the paw behaved similarly to the fin ger or toe pulps in man, sites of arteriovenous perfusion with high ba sal flow and a marked increment with thermal stimulation. In diabetic rats of both species, there was significantly lower flow at the back a nd base of tail than in non-diabetic animals. The differences were of the order of 30-40%. As a function of time, the decrease in blood flow at the base of tail parallelled the increase in glycohaemoglobin leve ls in the diabetic rats. In contrast, blood flow at the plantar surfac e of the paw was unchanged throughout the 3-month post-streptozotocin observation period. The decreases seen in blood flow were primarily du e to decreases in the velocity rather than the volume component of flo w. We conclude that there is an early phase of skin blood flow reducti on in the diabetic rat. The reduction in skin blood flow is found at n utritively perfused skin sites but not at areas with arteriovenous ana stomotic predominance.