Contractility and electrophysiological parameters of cremaster muscles of boys with a hernia or undescended testis

Background/Purpose : The cremaster muscle (CM) has been considered to participate in regulation of blood flow and temperature of the testis. Its contribution to testicular descent has been suggested. However, there is limited information about the CM in physiological and pathological states. Therefore, an experimental study has been conducted to evaluate and compare the contractile and electrophysiological properties of CM in boys with descended or undescended testes. Methods : Identical CM strips were obtained from eight boys who underwent orchidopexy with a mean age of 3 ± 2.2 years and from eight boys who underwent herniorrhaphy with a mean age of 4 ± 1.3 years. Muscle strips of 3 × 8 mm were vertically attached to an isometric force displacement transducer, and direct muscle contractions were elicited by rectangular electrical pulses. Direct isometric muscle contractions were recorded in an organ bath containing mammalian Ringer's solution. In electrophysiological experiments, conventional microelectrode techniques were used. Results : Direct electrical stimulation of CM strips obtained from patients with descended and undescended testes elicited muscle twitches and frequency-dependent contractile responses. Tetanic contractions of undescended testes at 100 Hz were 67% greater in amplitude than that of descended testes ( P < .002). Muscle strips of both groups exhibited increased twitch amplitudes by 105% ± 37% when the temperature of the bathing solution was increased from 22° to 37°C ( P < .001). The electrophysiological findings were similar. Conclusions : Contrary to other striated muscles, elevated temperature increases the contractility of CM. If the increased contractility by an increase in temperature is a property unique for CM, it should reflect the attempts at regulating testicular blood flow or temperature. The increased amplitude of contractions encountered among the CM of boys with undescended testis suggests the CM to have a role on the location of the testis.