The effect of aging on skin blood flow in the Wistar-Kyoto rat

Using laser Doppler techniques in man, we have previously demonstrated that skin blood flow decreases linearly with age. In previous work, we have shown similarities in skin blood flow properties between man and the rat. Our goal was to assess a possible aging effect of skin blood flow in the rat. We determined skin blood flow sequentially in 13 Wistar-Kyoto rats, beginning at 3 months of age, then at 6, 12, 15, and 18 months. We measured flow on the back, the base of the tail, the upper leg, all nutritively (NUTR) perfused sites, and on the plantar paw surface, which is perfused chiefly by arteriovenous anastomotic (AVA) capillaries. We measured flow, microvascular volume and red blood cell velocity at basal temperature and also heated the skin locally to 44 degrees C, to elicit maximal vasodilation. Skin blood flow declined in a linear fashion with increasing age. The decrease was in the order of 15% over 18 months and occurred at both NUTR sites and the paw. The decrease was due to reduced microvascular volume, presumably representing loss of skin capillaries. Red blood cell velocity was not reduced; in fact, it was significantly increased at several NUTR sites. The WKY rat provides an excellent model of aging of the skin microvasculature. The changes we have demonstrated, while not identical to those we have previously demonstrated in man, are sufficiently similar to permit further exploration of the mechanisms of these changes.

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 skin blood flow is reduced in Type 1 (insulin-dependent) diabetic patients. The possibility of using the skin as an extremely accessible indicator of diabetic microvascular disease is attractive. The streptozotocin diabetic rat is an appealing potential animal model. We performed measurements of skin blood flow in two rat species, nine Sprague Dawley (SD) rats and nine Wistar Kyoto (WKY) rats, observing early changes following the inception of diabetes. Four of the SD rats and five of the WKY rats were made diabetic, the rest serving as controls. There were no significant differences in skin blood flow between the two rat strains. As in man, there appear to be rat skin sites with primarily nutritive capillary supply and those with arteriovenous anastomotic predominance. The back and base of tail, both hair-covered areas, demonstrated low flow characteristics, consistent with nutritive perfusion. In contrast, the plantar surface of the paw behaved similarly to the finger or toe pulps in man, sites of arteriovenous perfusion, with high basal flow and a marked increment with thermal stimulation. In diabetic rats of both species, there was significantly lower flow at the back and 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 levels in the diabetic rats. In contrast, blood flow at the plantar surface of the paw was unchanged throughout the 3-month post-streptozotocin observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Skin blood flow in the Wistar-Kyoto rat and the spontaneously hypertensive rat

1. Using laser Doppler techniques in man, we have previously demonstrated differences in skin blood flow properties at sites with primarily nutritive (NUTR) perfusion, such as the elbow or knee, as compared to sites such as the finger pulp, with predominantly arteriovenous anastomotic (AVA) perfusion. 2. Basal and heat stimulated flow is greater at AVA sites. In man, blood pressure changes are reflected primarily by changes at AVA rather than NUTR sites. 3. These blood pressure induced changes affect the red blood cell velocity (VEL) component at AVA sites more than microvascular volume (VOL). 4. Given these findings in man, we decided to compare skin blood flow properties in a suitable animal model. 5. We chose the Wistar-Kyoto (WKY) and Spontaneously Hypertensive Rat (SHR) strains, in view of the marked difference in systemic blood pressure in these two related strains. 6. Skin blood flow varied considerably at different skin sites in the rats. Skin sites with hair covering, on the back and at the base of the tail, showed low basal and heat stimulated blood flow. 7. In contrast, the plantar surface of the paw behaved similarly to the finger or toe pulps in man, with 3-4-fold higher basal flow than the hair covered areas and a 7-8-fold rise with local heating to 44 degrees C. 8. Furthermore, there was a 25% greater blood flow at the plantar paw surface in the SHR rats as compared to the WKY rats, corresponding to the 25% higher systemic blood pressure in these animals. 9. The heat induced increase in flow at the plantar surface of the paw was primarily a result of a marked increase in VEL rather than VOL. 10. The higher flow at this site in SHR as compared to WKY rats was likewise ascribable to an increase in VEL, VOL being equivalent in the two strains.