Humoral Regulation of Renal Growth

Abstract

The stimuli for compensatory renal growth following a decrease in functioning renal mass have interested a number of investigators. The existence of a humoral incitor and/or regulator of renal growth, renotropin, has been postulated; and three types of experiments have been performed to determine its existence. These include parabiotic, in vivo, and in vitro assays. In general, the three different methodologies support the existence of a renotropic factor (or factors) but further investigations are needed to clarify its precise roles in compensatory renal growth.

Plasma from Uninephrectomized Rats Increases ³²P Incorporation into Phospholipids of Renal Cortical Slices

“…These data are in general accord with the observations on the effect of plasma or serum from uni nephrectomized rats on the in vitro enhancement in dry mass, number of mitoses, protein contentand radioactive labeling of nucleic acids [2,10,15,18]. The lack of any detectable change in acid-soluble radioactivity and in fluid spaces sussgests that the increase in labeling of phospholipids was not likely to be caused by changes in the levels of specific activities of precursor pools, but that it is more probably resulted from a specific alteration in phospholipid metabolism.…”

“…The results obtained in vivo [3] showed that incorporation of 32P into phospholipids and RNA was increased by 25-35% between 20 and 72 h after uninephrectomy. Compared with these results, the shor ter duration of increased incorporation o f32P into phos pholipids observed here may indicate that the presence of intact (functionally capable) renal tissue is needed for complete expression of humoral renotropic factor(s) ac tivity [2], An increased 3H-thymidine incorporation into DNA was reported when larger amounts of serum from uni nephrectomized animals were added to incubation me dia with renal cortical slices [15] or to primary rabbit kidney cell culture [10,18], In general agreement with this finding a graded response in labeling of PA and PI was observed here with different amounts of plasma ( fig. 3).…”

“…This apparently resulted from increase in the Vm;is of choline kinase and choline phosphotransferase reac tions without a change in the apparent Kn, of either enzyme [8], In experiments in vivo, using carrier-free 32P we observed an increased labeling of phospholipids, par ticularly of phosphatidic acid (PA) and phosphatidylinositol (PI) in the kidney remaining after unilateral neph rectomy [3]. Normal renal tissue incubated with plasma or sera from uninephrectomized animals exhibited an enhancement in dry mass, number of mitoses, protein content and radioactive labeling of nucleic acids [2,10,15,18]. To investigate the possible involvement of humoral factor(s) in the alteration of phospholipid metabolism during compensatory kidney growth the controlled con ditions of an in vitro system was used in the present investigation.…”

Transferable circulating factors and epithelial sodium transport after unilateral nephrectomy in the rat.

“…Specifically, insulin-like growth factor-1, epidermal growth factor and hepatocyte growth factor have been considered to play an aetiological role. The existence of a further circulating factor, a kidney-specific 'renotropin' which remains unidentified, has been established by serum injection into live animals, cross-circulation studies and in vitro assays (Austin, Goldin & Preuss, 1981 1251-human a-ANP (1O00 #1) was added to all tubes, which were then vortexed and incubated at 4°C for 24 h. Goat anti-rabbit IgG (1005ul) was added to all tubes followed by normal rabbit serum (100 ,ul). All tubes were vortexed and incubated for 2 h at room temperature.…”

Stimulation of Thymidine and Uridine Incorporation into Rat Renal Cortical Cells in Primary Monolayer Culture by Uninephrectomized Rat Serum

“…Recent reports indicate the presence of humoral factors in plasma that stimulate the uptake of thymidine or uridine into the renal cells or in crease the protein contents of renal tissue in vitro [1]. The characteristics of this renotropic factor, however, are not yet fully elucidated.…”