[The effects of gravity load on the canine kidney]

In Self-defense Force Hospitals we often treat pilots with renal stones who will be exposed to high gravity (G) load after the treatment. Because the regulation prohibits the flight of a pilot with urolithiasis, the stone must be removed completely by noninvasive procedure. Percutaneous nephrolithotomy, therefore, is one of the treatment of choice in such patients. The effect of G load on the kidney, in particular, on the renin-angiotensin-aldosterone (R-A-A) system and the safety of percutaneous nephrolithotomy in a pilot who is exposed to high G load have not been adequately investigated. In this study, I examined the effect of G load in canine kidney model. The effect of G load on R-A-A system: Twenty-two adult mongrel dogs of a mean weight of 10.9 kg. maintained on a normal Na+ intake were studied. To dogs in the sitting position, high G load was given. The exposure to G load consisted of maximum load of 8 G for 45 seconds with the onset ratio of 0.1 G/sec. for group 1, and 5 courses of maximum G load of 8 G for 10 seconds with the onset ratio of 2.5 G/sec., followed by 1.5 G for 60 seconds for group 2. Plasma renin activity was unchanged in group 1, but it increased in group 2. Plasma aldosterone increased from 68.6 +/- 17.9 to 252.0 +/- 56.4 pg/ml (p less than 0.005) in group 1. and from 191.8 +/- 40.6 to 479.2 +/- 76.0 pg/ml (p less than 0.005) in group 2 after G load. Angiotensin II decreased from 129.0 +/- 19.4 to 84.7 +/- 19.1 pg/ml (p less than 0.05) after G load in group 2. These data suggest that the increase in plasma aldosterone after G load in independent of the renin-angiotensin system. It is considered that the alteration of R-A-A system was caused by the change of blood flow distribution due to the effect of G load. The tolerance to G load on the kidney following subcutaneous nephrostomy: Unilateral subcutaneous nephrostomies were carried out under pentobarbital anesthesia in 15 adult female mongrel dogs. Each experimental dog was exposed to high G load 2 or 4 weeks after removal of the nephrostomy tube. Excretory urography, renal angiography and renal function tests were performed before and after G load. Excretory urograms demonstrated no remarkable changes at all after G load in all dogs. Renal angiograms revealed small renal infarction along the nephrostomy tract in almost all dogs.(ABSTRACT TRUNCATED AT 400 WORDS)