J. Biol. Chem., Vol. 262, Issue 23, 11156-11162, Aug, 1987
Radioimmunoassay for testicular cytochrome c (ct). Evidence for the presence of apocytochrome ct pool in rat testis extract
IC Kim
Mammalian testis contains a tissue-specific testicular cytochrome c (cyt
ct). By immunizing rabbits with rat cyt ct and phosphorylated albumin
(pBSA), rabbit anti-cyt ct was produced. Then the antiserum was applied to
phosphorylated bovine serum albumin and rat somatic cyt c (cs)-Sepharose
affinity columns to remove cross-reacting antibodies. The resultant
anti-cyt ct was highly specific for cyt ct. From immunoblot assays, no
protein other than cyt ct in rat testis extract was bound by the anti-cyt
ct. By using the anti-cyt ct, radioimmunoassay (RIA) was developed for the
quantitation of cyt ct in rat testis extract. The observation that the RIA
did not bind rat cyt cs (1-1000 pmol), and other rat tissue extracts
(kidney, heart, lung) further indicated that the RIA was highly specific
for rat cyt ct. Separately, the concentration of holocyt ct was determined
using CM- cellulose chromatography and subsequent spectral analysis on the
same testis extract. The total cyt ct concentration in the rat testis
extract determined by the RIA was about 3-fold higher than those determined
by the latter techniques. Since the affinity purified anti- horse cyt c
cross-reacted with both horse holo- and apocyt c, anti-rat cyt ct will
cross-react with rat apocyt ct. Thus the concentration of cyt ct
quantitated by the polyclonal anti-cyt ct-based RIA probably included
apocyt ct concentration as well. Therefore, the higher cyt ct concentration
determined by the RIA was probably attributed to the presence of the apocyt
ct in the testis extract. The presence of the high concentration of the
apocyt ct pool in testis is probably necessary to maintain continuous
spermatogenesis, during which holocyt ct is incorporated into sperm
mitochondria.