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Factors affecting the development of the processus vaginalis in the rat
T D Clarnette1, J M Hutson, S W Beasley
1F. Douglas Stephens Surgical Research Laboratory, Royal Children's Hospital, Melbourne, Victoria, Australia.
Purpose:
We examined the factors that influence development of the processus vaginalis in the rat.
Materials And Methods:
Neonatal Sprague-Dawley rats 0 to 3 days old underwent distal or proximal gubernaculotomy, unilateral orchiectomy or proximal genitofemoral nerve transection. At ages 28 to 60 days the rats were sacrificed, position of the testis was noted and length of the processus vaginalis was measured.
Results:
There was no development of the processus vaginalis after distal gubernaculotomy. Proximal gubernaculotomy enabled the processus vaginalis to achieve a mean length similar to that of controls (p = 0.06) when the testis descended into the scrotum. Mean length of the processus after proximal gubernaculotomy with an abdominal testis, surgical orchiectomy and torsion of the testis after proximal gubernaculotomy was similar (p = 0.9) but less than that of controls (p < 0.05). Proximal division of the genitofemoral nerve produced variable results depending on how and when the surgical procedure was performed, and whether the psoas muscle was divided.
Conclusions:
Distal attachment of the gubernaculum is essential for normal development of the processus vaginalis. Distal gubernaculotomy prevents development of the processus vaginalis because of mechanical disruption of the gubernaculum. Proximal attachment is not essential for normal development of the processus vaginalis but it serves to anchor the testis to the region of the internal inguinal ring, allowing intra-abdominal pressure to facilitate descent of the testis. In the presence of an innervated gubernaculum the processus vaginalis achieves greater length when the testis descends into the scrotum, suggesting that its complete development demands the presence of a testis in the sac. The timing of genitofemoral nerve division may be crucial in determining the subsequent effect on the development of the processus vaginalis and testicular descent, since programming of the gubernaculum by calcitonin gene-related peptide released from the genitofemoral nerve appears to occur just before birth in the rat.