Biomedical subjects

O Collin

Publications and source records attributed to O Collin.

22 records · Page 2Linked to original sources

PubMedDate not supplied

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 (r(s) = 0.39, r(s) = 0.82, r(s) = 0.64, respectively, P < 0.001), and they were all correlated with systemic blood pressure (r(s) 0.41, r(s) = 0.61, r(s) = 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 (r(s) = 0.58, r(s) = 0.75, r(s) = 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.

Activity Cycles↗

PubMedDate not supplied

Effects of endothelin-1 on the rat testicular vasculature.

Endothelin-1 (ET-1), a well-known vasoconstrictor substance, is present in the testis but its functional role is unknown. The present study was undertaken to elucidate whether ET-1 may influence testicular blood flow. ET-1 (0.1, 1, 10, 100 ng), an ETA antagonist (BQ123; 0.01, 1, 100 micrograms), or saline were administered by intratesticular injections (0.1 ml) in adult rats. The effect on testicular blood flow was monitored using a laser Doppler flowmeter. The localization of immunoreactive ET-1 (irET-1) was studied by immunohistochemistry and the testicular irET-1 concentration was measured in normal and human chorionic gonadotrophin (hCG)-treated rats using a radioimmunoassay. ET-1 injection, in a dose-related way acutely decreased testicular blood flow and this effect was blocked by an ETA antagonist. The antagonist itself did not, however, influence testicular blood flow. Accumulation of polymorphonuclear leukocytes was observed in testicular venules 2 hours after ET-1 injection. Immunoreactive ET-1 was observed in Leydig, Sertoli, and endothelial cells. The testicular irET-1 content was increased 2-fold by hCG stimulation but local injection of the ET-1 antagonist did not influence testicular blood flow in hCG-treated rats. The present study suggests that ET-1 could be a hormonally regulated and locally produced modulator of testicular blood flow and microcirculation.

Animals↗

PubMedDate not supplied

Localization and effects of calcitonin gene-related peptide in the testicular vasculature of the rat.

UNLABELLED: Using laser Doppler flowmetry, the effects of unilateral intratesticular injection of calcitonin gene-related peptide (CGRP) and CGRP8-37, a CGRP-receptor antagonist, on right- and left-testicular blood flow and mean arterial pressure were studied on anesthetized adult rats. Calcitonin gene-related peptide in doses of 5 and 50 ng increased blood flow 37 +/- 11% (mean +/- SEM, P < 0.05) and 30 +/- 5% at 5 mm, but not 15 mm, away from the injection site, respectively. They did not influence mean arterial pressure nor blood flow in the contralateral testis. Five-hundred nanogram doses increased testicular blood flow in the injected testis at a point 15 mm away from the injection site (22 +/- 3%, P < 0.05) and caused a slight decrease in mean arterial pressure (-12 +/- 3%, P < 0.05). The highest dose, 5 micrograms, caused a large (-39 +/- 3%, P < 0.05) fall in mean arterial pressure within 1 minute after injection, and testicular blood flow was reduced in both the injected (-9 +/- 2%, P < 0.05, 15 mm away from injection site) and contralateral testis (-20 +/- 5%, P < 0.05). Pretreatment with 500 ng of the receptor antagonist, CGRP8-37, did not significantly attenuate the blood flow increasing affect of 50 ng CGRP, nor did 50 micrograms CGRP 8-37 (given alone) influence basal testicular blood flow in the injected testis. Using Immunohistochemistry, CGRP-containing nerves were observed in the superior and interior spermatic nerves, in the testicular artery, and in the veins leaving the testis but not in intratesticular blood vessels. CONCLUSIONS: 1) CGRP is a potent vasodilator in the testicular vasculature and it may be involved in the local regulation of testicular blood flow: 2) the testis has limited capacity to autoregulate and is consequently unable to maintain a constant testicular blood flow during large and rapid reductions in blood pressure, and 3) the local and systemic effects of vasodilators act in opposite directions in the testis.

Animals↗

PubMedDate not supplied

Unilateral injection of neuropeptide Y decreases blood flow in the injected testis but may also increase blood flow in the contralateral testis.

Neuropeptide Y (NPY) receptors have recently been described in intratesticular arterioles, but the role of NPY in testicular blood-flow regulation has not been examined. To explore this, we administered NPY in various doses (0.01-10 microg) via intratesticular injections and studied testicular microcirculation using a laser Doppler flow meter. NPY injection shows a dose-response pattern, with 1 microg (the most potent dose) causing a decrease (-42.4 +/- 3.7%, P < 0.00005) in blood flow in the ipsilateral testis of all the animals and an increase in blood flow in the contralateral testis (+17.2 +/- 5.6%, P = 0.03, n = 25 animals). The response in the contralateral testis was variable. A clear-cut increase was seen in 19 of the 25 animals examined, whereas either no response or a slight decrease was seen in the remaining six. The contralateral increase, which was not seen in the hindpaw on the same side, did not occur when the neuronal connections to the testes were blocked by injection of local anesthetics into the spermatic cord, either on the NPY-injected side or on the contralateral side. Our results suggest that NPY may serve as a vasoconstrictor in the testis, probably by acting on the NPY-Y1 receptors present on intratesticular arterioles. Local injection of NPY causes a major decrease in blood flow in the injected testis. This decrease is followed in the majority of animals studied by an increase in blood flow in the contralateral testis, an effect that seems to depend on neuronal mechanisms. This observation suggests that the testes may communicate under certain situations. The functional consequences of this remain to be elucidated.

Animals↗