Hemodynamic Mechanism of Erection in the Human Penis

Abstract

M. SHIRAI," N. ISHII, S. MITSUKAWA, S, MATSUDA, and M. NAKAMURA Six infertile patients and one patient with ureteral calculus were studied to elucidate the intrapenial hernodynamics of erection. Xe-133 was infused into the corpus cavernosum and visual sexual stimulation (V.S.S.) provided to induce erection. Xe-133 clearance curves declined at a uniform rate in the nonerect penis without V.S.S. Xe-133 clearance curves for five patients with complete erection at V.S.S. indicated a sudden drop upon erection. Unlike previous reports, it was noted that penial erection can occur independently of a venous-return blocking mechanism.

Pre-penile arteries are dominant in the regulation of penile vascular resistance in the rat

“…This occurs through changes in the contractile state of the vascular smooth muscle of the arterio-venous system which includes all the pre-sinus and pre-capillary arteries and arterioles in addition to well recognized changes in helicine arteries and sinuses. 6 ± 8 Hemodynamic studies in dogs 8,9 and in normal young men 10 have shown that an erectile stimulus provokes a large and transient increase in intracavernosal arterial in¯ow. Other specialized vascular beds have been studied and a signi®cant role for feeder vessels that respond directly to changes in metabolic demand has been identi®ed.…”

Use of radioactive tracers in the evaluation of penile hemodynamics: history, methodology and measurements

“…With the exception of Shirai et al, 29 the majority of investigators have found that normal erection results in decreased penile washout, while in patients with venous disease, more rapid washout occurs, ®ndings that ®t in well with current models of penile hemodynamics. Multiple explanations have been suggested to reconcile Shirai et al's 29 anomalous results with the more comprehensible consensus ®ndings.…”

“…Multiple explanations have been suggested to reconcile Shirai et al's 29 anomalous results with the more comprehensible consensus ®ndings. 29,30,33±35 Their common denominator is the understanding that erection is a dynamic process and measurement at different times will give highly variable results, compounded by the fact that degree of erection is itself variable, depending on the type and effectiveness of stimulus employed. Measurements under different clinical conditions, and with different stimuli, could conceivably produce very disparate results.…”

“…30 In ®ve subjects with complete erections after VSS, Shirai 29 found that intrapenile blood¯ow averaged 2.0 mla100 gmamin whilē accid and 43.0 mla100 gmamin while erect, assuming a partition coef®cient of 1. Because the basic mechanisms of erection were not established, this suggested to Shirai that venous occlusion is not a normal component of erection.…”

“…Intracavernosal 133 Xe injections, to determine cavernosal blood¯ow, were ®rst described in 1978 by Shirai and coworkers 29 and in 1980 by Wagner and Uhrenholdt. 30 In ®ve subjects with complete erections after VSS, Shirai 29 found that intrapenile blood¯ow averaged 2.0 mla100 gmamin whilē accid and 43.0 mla100 gmamin while erect, assuming a partition coef®cient of 1.…”