Effect of epinephrine on vascular space of gills and head of rainbow trout

The filling of the gills and head vascular space of a teleost fish was measured in vitro by perfusing an isolated head of a trout with a Ringer solution containing 131I-labeled human serum albumin. The presence of epinephrine in the Ringer solution significantly increased afferent (ventral aortic) flow rate and efferent (dorsal aorta) flow rate, whereas branchial venous system circulation was reduced. When perfused with an epinephrine-free Ringer, the branchial vascular space appears 5-6 times greater than the head vascular space (per 100 g of tissue). Epinephrine, 10(-5) M, in the Ringer solution significantly decreased the branchial vascular space without modifying that of the head. The increase in perfusion rate and decrease in branchial vascular space due to the epinephrine can only be interpreted by taking into account a branchial nonlamellar compartment of a considerable volume.