Application of corrosion casting procedures in identification of perfusion distribution in a complex microvasculature

The effects of vasoactive molecules on perfusion distribution within the microvasculature of the fish gill filament was examined by scanning electron microscopic analysis of methyl methacrylate corrosion casts. Gills from the channel catfish, (Ictalurus punctatus) were preperfused with a Ringer solution containing either epinephrine (10(-5)M), acetylcholine (10(-6) or 10(-8)M) or sodium nitroprusside (10(-5)M). The preperfusion was followed immediately by the methyl methacrylate resin, Mercox. All perfusion was done at physiological pressures. Epinephrine increased filling of the respiratory vasculature and favored central filamental filling on the efferent side of the filament. Acetylcholine at high doses (10(-6)M) greatly decreased respiratory vessel filling and favored filling of the central vessels on the afferent side. At low doses (10(-8)M) acetylcholine reduced respiratory filling and greatly increased methacrylate filling of the central filamental vessels. Nitroprusside decreased resin in both respiratory and central filament vessels. Sphincter like constrictions in the corrosion replicas identified vasoactive sites in acetylcholine perfused gills. The results demonstrate the applicability of this technique in identification of perfusion regulation in a complex, multifunctional vascular bed. Possible sources of error of this technique include vasostimulation by methyl methacrylate and viscosity effects.