Elevated concentrations of beta-nerve growth factor in selected tissues from senescence-accelerated mice (SAM-P/8)

Levels of the beta-subunit of nerve growth factor (beta-NGF) were determined in various tissues from senescence-accelerated mice (SAM-P/8) and compared with those from senescence-resistant control mice (SAM-R/1) at 4 months of age. (1) In SAM-P/8, the testis was 30% larger in terms of wet weight than that from SAM-R/1, whereas the adrenal glands from males and females were smaller than those from the respective controls by 45% and 20%, respectively. (2) About 70% of SAM-P/8 individuals had high concentrations of testosterone in serum (greater than 5ng/ml). (3) In SAM-P/8, endogenous levels of beta-NGF were significantly higher in the adrenal gland (20 and 7 times higher on average in males and females, respectively), in the thymus (100 and 5 times higher in males and females, respectively) and in the testis (500 times higher) than those in the control tissues. In other tissues there were little or no differences in terms of levels of beta-NGF. (4) Morphological changes in the adrenal gland, thymus and testis of SAM-P/8 mice were not as marked as expected from the elevated levels of beta-NGF in these tissues. (5) These results show that, in SAM-P/8 mice at 4 months of age, an elevation in the endogenous level of beta-NGF has already occurred in some peripheral tissues before senescence becomes accelerated.