Testicular microcirculation in the rat studied by videophotometric capillaroscopy, fluorescence microscopy and laser Doppler flowmetry.

Testicular capillary blood flow was studied in rats using laser Doppler flowmetry, in vivo fluorescence microscopy and videophotometric capillaroscopy. All the methods revealed rhythmical oscillations in testicular microcirculation with a periodicity of 4-10 c.p.m. In arterioles, capillaries and small post-capillary vessels, periods of continuous blood flow alternated with periods of no or very low flow. No visible leakage of dextran-150 was observed from the testicular blood vessels. Four, 8 and 16 h after an s.c. injection of 200 IU hCG the blood flow was continuous and there was leakage of dextran-150 from the microvessels to the interstitial tissue. Twenty-four and 32 h after hCG the blood flow pattern was again rhythmical, and at 32 h there was no leakage of dextran-150. This suggests that hCG induces changes in blood flow and transvascular fluid exchange in the testis, perhaps by altering smooth muscle activity at the arteriolar-level.