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GENDER DIFFERENCES IN ONE YEAR OLD DAHL SALT-SENSITIVE AND -RESISTANT RATS.   D.P. Cappiello¹, S.R. Locklear¹, M. Thierry-Palmer² and S.B. Arnaud^{1   1}NASA Ames Research Center, Moffett Field, CA and ²Morehouse School of Medicine, Atlanta, GA.

     We raised male and female Dahl Salt-sensitive (SS) and -resistant (SR) rats to 12 months of age on normal sodium diets of 0.36% - 0.4%, in the course of studies using these animals as a space flight model. We noted increased mortality in males. Male and Female SS and SR groups were born in the same week. Females were sacrificed at age 349 days and males 27 days later. There were 12 males, 7 SR and 5 SS; 11 females, 6 SR and 5 SS. Average ("SD) male SR BW at time of necropsy was greater than twice SR female BW (485"39g vs. 210"5g, p<0.001), as well as male SS vs. female SS (447"26g vs. 254"26g, p<0.001). Organ weight comparisons were calculated in terms of g/100g grams of BW. Gender differences revealed female SS rats had larger hearts (0.436"0.02 vs. 0.296"0.02, p<0.05), and smaller livers (2.426"0.15 vs. 3.13"0.21, p<0.05), as compared to male SS rats. Male SS kidneys were larger than female SS kidneys (0.428"0.07 vs. 0.354"0.02, p<0.05). Male SR kidneys were smaller than female SR kidneys (0.277"0.02 vs. 0.352"0.04, p<0.05). Comparisons of SS and SR BW showed no differences in males. Kidneys were the same in females, but not in males, p<0.05. Male SS compared to SR rats displayed larger hearts (0.370"0.08 vs. 0.296"0.02, p<0.05), larger spleens (0.349"0.11 vs. 0.188"0.01, p<0.05), and larger kidneys (0.428"0.07 vs. 0.277"0.02, p<0.05). There were no differences in relative organ weights between female SS or SR groups. It is unlikely that the 27-day earlier necropsy of females than males accounted for the lack of differences in the female groups. These data suggest that male Dahl rats are more prone to aging effects associated with higher mortality in males.   

     (Supported by NASA NAG2-1381)