Is there any tubular secretion of protein?

Immunohistological investigations performed with the PAP method on tubular casts in the thick Henle loops and in the distal convoluted tubules led to the following results. 1) In control kidneys, casts consisting of sIgA and IgM occur, mostly isolated, in 30% and 20%, respectively, of cases. On the other hand IgG casts, likewise isolated, are only observed in 7% of cases. 2) In the case of mesangioproliferative glomerulonephritis of the IgA and non-IgA nephritis type, casts consisting of sIgA and IgM are observed more often than in control kidneys, especially when the serum creatinine concentration exceeds 1.3 mg%; i.e., the glomerular filtration is reduced. 3) In kidneys with inflammatory and non-inflammatory glomerular diseases which had led to nephrotic syndrome, casts consisting of sIgA and IgM are not observed more often than in kidneys with glomerulonephritides which had not been accompanied by nephrotic syndrome. 4) In kidneys with severe impairment of the excretory function (rapidly-progressive glomerulonephritis, primary malignant nephrosclerosis, acute renal failure) casts consisting of sIgA and IgM are observed more often than in controls but not more often than in IgA and non-IgA nephritides with increased serum creatinine concentration. 5) In kidneys which had become aglomerular as a result of scarring of the glomeruli, with atrophic proximal tubules and preserved epithelia of the ascending loop of Henle, casts consisting of sIgA and IgM as well as secretory component occur in a large quantity.(ABSTRACT TRUNCATED AT 250 WORDS)