Microfilaments and intermediate filaments (Ifs) represent an important components of the cytoskeleton. In mammals including rats, peritubular myoid cells (PMCs) contain alpha smooth muscle actin (ct-SMA) micro-filaments, while sertoli cells contain intermediate filaments vimentin. Pre­vious studies mentioned some as­pects about the distribution of these filaments in these cells, however little was mentioned about the changes in their distribution during postnatal (p.n) development.
In the present study, immunohisto-chemical methods were used to de­tect the changes in distribution of a-SMA in PMCs and vimentin in sertoli cells during postnatal development of rat testis (one day,7 days,14 days,28 days.42 days and 56 days) a- SMA immune reaction was seen early from the 1 st day of p.n age in few PMCs. On p.n day 7. there was increase in PMCs exhibiting +ve a-SMA immune reaction. This reaction was well established around the whole circumference of the seminifer­ous tubules on p.n day 14 and the adult distribution pattern was seen on p.n day 28. Intermediate filaments (Ifs) vimen­tin were mainly observed at the basal nuclear region of few sertoli cells on p.n day 7 and the first appearance in supranuclear or apical region was on p.n day 14.