ROLE OF INTRACELLULAR CA2-MUSCLE OF HUMAN PENILE ERECTILE TISSUE( STORES IN SMOOTH)

Objective: In human erectile tissue smooth muscle contraction and detu mescence are highly dependent on an increase in cytosolic [Ca2+]. The Ca2+ influx can be derived from the extracellular space or from intrac ellular sarcoplasmic stores. The role of both pathways was evaluated i n an organ bath study on human cavernosal strips. Patients and methods : The tissue was obtained from 12 patients with chronic erectile dysfu nction. The effects of Ca2+-free solution, ryanodine, caffeine and of nifedipine on electrically and adrenergically induced contractions wer e evaluated. Results: Following an incubation period of 10 min in Ca2-free solution the electrically induced contraction was reduced to 20% , whereas the contraction induced by phenylephrine (PE) was only reduc ed to 64 +/- 6% (mean +/- SEM). Ryanodine inhibited the PE-contraction to 30 +/- 6% and the additional application of caffeine or nifedipine further reduced the contraction to 11% and 8%. Conclusion: The result s give evidence for a role of intracellular Ca2+-stores in human caver nosal tissue. Whether the more marked effect of ryanodine in tissue fr om patients with erectile failure in comparison with similar experimen ts in rabbit cavernosal tissue might be a sign of an increased caverno sal contractility in these patients remains to be shown in future expe riments with normal erectile tissue.