The mesenteries of ten cats (0.6 kg) anesthetized with Dial-
urethane were exposed and studied using fluorescence television microscopy. Femoral artery pressure was determined.
FITC-dextran, the plasma label, or
DTAF-labeled red cells (
DTAF-RBCs) were injected as a bolus (0.005 ml in 0.5 sec) into a small branch of the mesenteric artery. Animals were hemorrhaged from the left femoral artery into a reservoir. Control mean arterial pressure averaged 100 +/- 2 mmHg and decreased to 84 +/- 1 mmHg subsequent to an average bled volume of 13 ml/kg. Time-concentration curves were recorded from videotape recordings of the passage of
indicator by videodensitometry. Following
hemorrhage, arteriolar (N = 134)
FITC-dextran mean transit time (t) was increased significantly to 194 +/- 10% of control, while t for
DTAF-RBCs increased significantly to 211 +/- 10% of the control value. In the venules (N = 180)
hemorrhage significantly increased
FITC-dextran t to 197 +/- 9% of control while venular
DTAF-RBC t was significantly increased to 182 +/- 5% of control. Arteriolar t was significantly lower for
DTAF-RBC than for
FITC-dextran during the control period and following reinfusion. Following
hemorrhage, arteriolar t for
DTAF-RBCs was not different from that for
FITC-dextran. Venular values were significantly lower for
DTAF-RBCs than
FITC-dextran during all three periods. Dispersion was increased (reduced ta/t) by
hemorrhage in arterioles and venules. The elevated t after
hemorrhage would appear to be the result of increased peripheral resistance and resulting reduced flow velocity through the circuits. The absence of a difference in arteriolar t between the two indicators post-
hemorrhage would indicate reduced Fahraeus effects owing to reduced blood flow velocity and perfusion pressure.