RENAL SINUS LIPOMATOSIS AND BODY-COMPOSITION IN HYPERTENSIVE, OBESE RABBITS

OBJECTIVE: To test whether renal lipomatosis, an accretion of fat in t he renal sinus associated with chronic renal infections, abscesses and calculi, can also be caused by rapid weight gain. DESIGN: New Zealand white rabbits were fed either standard rabbit chow (n = 24) or chow f ortified with 10% corn oil plus 5% lard (n = 25) for 8-12 weeks. MEASU REMENTS: The rabbits and constituent tissues were weighed initially, a fter drying and after organic extractions. Renal tissue cholesterol an d triglycerides were measured chemically. RESULTS: Rabbits made obese by increased fat intake were 1.8 kg heavier than controls (5.5 +/- 0.3 kg vs 3.7 +/- 0.2; n = 24,25), had 1.54 kg more body fat (1.90 +/- 0. 25 vs 0.36 +/- 0.11 kg/rabbit; n = 10,9), and had a mean arterial bloo d pressure that was 9.2 mm Hg greater than controls (95.1 +/- 8.5 vs 8 5.9 +/- 5.6 mm Hg; n = 23,24). Individual organs grew in mass (lung, 1 5%; gastrocnemius, 17%; liver, 27%; kidney, 30%) and their parenchyma gained extractable lipids (lung, 5.5 mg/g tissue; gastrocnemius, 9.6 m g/g tissue; liver, 17.9 mg/g tissue). Total renal triglycerides were i ncreased 2.1 fold, from 103 +/- 36 to 219 +/- 59 mg/kidney (n = 8,8), compared to the 5.3 fold increase in whole body fat. Renal cholesterol was increased 1.7 fold, from 7.5 +/- 1.1 to 12.7 +/- 2.9 mg/kidney, ( n = 8,8). Within experimental error, the sum of the total renal trigly cerides plus the total renal cholesterol equaled the net fat extracted from the renal sinus alone: 95 +/- 29 mg/kidney in lean rabbits and 2 53 +/- 71 mg/kidney in obese (n = 17,17). CONCLUSION: Obesity alone ca n cause renal lipomatosis. This increased volume of anatomically local ized fat may be sufficient to externally compress renal veins and lymp hatics, thus altering renal hemodynamic behavior.