Temporal variations in testicular microcirculation

Temporal variations in microcirculatory blood flow in the testis and blood pressure were examined in intact, pentobarbital‐anesthetized rats with a two‐channel laser Doppler flowmeter. The laser Doppler probes that measure local blood flow in a tissue volume of about 2 mm3 were placed either over the mid portion of the left and right testes or on the right testes 1 cm apart. Testicular microcirculation was characterized by a prominent vasomotion with a frequency of 5.3 ± 1.4 cycles per minute and with an amplitude of 73 ± 32% (mean ± SD) of the mean. In addition to this large and rapid variation in local blood flow, there were also major variations from minute to minute in the average blood flow, vasomotion frequency, and vasomotion amplitude at 40 and 53 minutes. Such variations in local blood flow, vasomotion frequency, and vasomotion amplitude were correlated with each other at two different sites on the same testis (rs = 0.39, rs, = 0.82, rs, = 0.64, respectively, P ± 0.001), and they were all correlated with systemic blood pressure (rs = 0.41, rs, = 0.61, rs = 0.32, respectively, P ± 0.001). Minute‐to‐minute variations in local blood flow, vasomotion frequency, and vasomotion amplitude were also correlated between the right and left testes (rs = 0.58, rs, = 0.75, rs, = 0.57, respectively, P ± 0.001). There are substantial temporal variations in testicular microcirculation. These variations are to some extent related to temporal changes in systemic blood pressure, but changes in the ultralocal environment are probably more important. The functional significance of, and the factors responsible for, local variations in testicular microcirculation remain to be elucidated.