The penis in diabetes: structural analysis of connective tissue and smooth muscle alterations in a rabbit model

OBJECTIVE • To assess the volumetric density of collagen, elastic system fibres and smooth muscle cells in the corpus cavernosum (CC), corpus spongiosum (CS) and tunica albuginea (TA) in the penis of diabetic rabbits.

• Twenty-six New Zealand white rabbits were used. Diabetes was induced at 8 weeks of age in 13 rabbits by i.v. injection of 100 mg/kg of alloxan. The remaining 13 rabbits served as a control group. After 10 weeks, the rabbits were killed using sodium thiopenthal. • Midshaft penile fragments were obtained and processed by routine histological techniques. Stereological analysis of collagen, elastic system fibres and smooth muscle was performed in 5-µm sections by using a M42 test grid system. • Data were expressed as volumetric density (Vv; %). Collagen organization was evaluated by Picrosirius red staining under polarization.

• In the TA of diabetic rabbits, thickness increased by 88% (P < 0.001) with an enhanced collagen turnover. Moreover, the elastic fibre content was 34% higher (P < 0.001). In the CC of diabetics, collagen was diminished by 45% (P < 0.001) with a more organized collagen. • The elastic fibres were decreased by 46% (P < 0.001). Diabetes induced a 11% increase in CS collagen (P < 0.024) with an enhanced collagen turnover. • Smooth muscle in the CC of diabetic rabbits was increased by 40% (P < 0.001), whereas, in the CS, it was decreased by a similar amount (P < 0.001).

• Penile tissues were affected differently by diabetes, possibly as a result of cellular heterogeneity. • These changes could have an impact on blood flow and tissue resistance, and therefore might adversely affect erection.