Mechanisms involved in contractile differences among cremaster muscles according to localization of testis

Background/Purpose: Evidence suggests differences in contractility in crema ster muscles (CM) associated with undescended testis caused by alterations of autonomic innervation. Contractile responses of CM to various pharmacolo gic agents were evaluated and compared according to the localization of tes tis. Methods: Samples of CM from boys with undescended testis or inguinal hernia were obtained. Twitch and tetanic contractions were recorded isometrically at 37 degreesC. Effects of verapamil, isoprenaline, calcitonin gene-relate d peptide (CGRP), substance P (SP) and N-omega-nitro-L-arginine (L-NNA) wer e investigated. Results were compared through 2-way analysis of variance, and P values less than .05 were considered to be different. Results: Verapamil alone signifi cantly (P < .05) decreased contraction amplitudes in CM from both sources; the decrease was more pronounced in CM from boys with inguinal hernia (P < .05). Although isoprenaline increased contraction amplitudes in CM associat ed with undescended testis (P < .05), CGRP and SP increased contraction amp litudes in CM associated with descended testis (P < .05). L-NNA increased c ontraction amplitudes in both groups (P < .05). The decrease of contraction amplitudes after verapamil displayed a similar pattern after isoprenaline, SP, and L-NNA. Verapamil-induced contractility decrease was more pronounce d after CGRP in both groups (P < .05). Conclusions: Sensitivity of CM to verapamil differs according to localizati on of testis. Isoprenaline enhances contractility by stimulating Na+-K(+)AT Pase in undescended testis without altering voltage-sensitive channel sensi tivity to verapamil. CGRP and SP increase contractility in inguinal hernia, and CGRP increases the sensitivity of voltage-sensitive Ca2+ channels to v erapamil in CM from both groups. Nitric Oxide (NO) exerts inhibitory action on CM contractility, and it is less pronounced in undescended testis. Thes e differences may contribute to pathophysiology of undescended testis. Copy right (C) 2001 by W.B. Saunders Company.