QUANTITATIVE MICROSCOPIC CHANGES IN THE MOLE-RATS ACCESSORY SEX-ORGANS DURING AN ANNUAL CYCLE

Background: The mole rat, Spalax ehrenbergi, is a solitary, aggressive subterranean rodent. The present study summarizes a year-round invest igation of morphological changes in the mole rat's accessory sex organ s. Methods: Mole rats maintained in the laboratory were killed after 3 months of acclimation; additional animals trapped in the wild were ki lled immediately. The accessory sex organs were processed for routine histological examination. Tissues were fixed in Bouin's solution, embe dded in paraffin blocks, and stained by hematoxylin-eosin. A systemic sampling approach was used to photomicrograph the tissues for histomor phometric assessment. Results: The volume fraction (Vv, mean +/- SEM) of prostate connective tissue from animals kept in captivity increased significantly in January (0.49 +/- 0.05 mm(3)/mm(3)) and April (0.43 +/- 0.04 mm(3)/mm(3)) but only 0.26 +/- 0.03 mm(3)/mm(3) in November. In the field group, the Vv of prostate connective tissue was significa ntly higher in January (0.58 +/- 0.08 mm(3)/mm(3)) and April (0.62 +/- 0.08 mm(3)/mm(3)) and lower in November (0.44 +/- 0.03 mm(3)/mm(3)) a nd February (0.43 +/- 0.03 mm(3)/mm(3)), with a concomitant decrease i n prostate tubuli and lumen. The prostate tubuli star volume (v) in l aboratory animals increased in November (0.009 +/- 0.002 mm(3)) and Ma y (0.09 +/- 0.02 mm(3)). The same pattern was shown in the field group , with a significant increase in December (0.012 +/- 0.002 mm(3)) and March (0.007 +/- 0.001 mm(3)). The Cowper tubuli Vv in the captive ani mals increased during February (0.24 +/- 0.02 mm(3)/mm(3)), with a con comitant reduction in the connective tissue (0.05 +/- 0.02 mm(3)/mm(3) ). The Cowper tubuli v in same animals increased in December, April, and July (1.37 +/- 0.18 x 10(-4) mm(3), 0.94 +/- 0.10 x 10(-4) mm(3), 1.52 +/- 0.20 x 10(-4) mm(3), respectively). In field group, a slight decrease in star volume took place from November to May (1.25 +/- 0.16 mm(3) to 0.39 +/- 0.05 mm(3), respectively). Testosterone levels appe ared to be higher in the field group than in the laboratory group. In December the values were 1.62 +/- 0.15 ng/ml in the field group and 0. 55 +/- 0.12 ng/ml in the laboratory group, and in May the laboratory g roup values were 1.66 +/- 0.12 ng/ml. Conclusions: In captivity and in the field, male mole rats probably undergo an annual cycle of accesso ry gland tissue structural changes that are correlated with testostero ne secretion. (C) 1996 Wiley-Liss, Inc.