Barbara Rennick

Pharmacology of smooth muscle valve in renal portal circulation of birds.

The avian renal portal system, first described by Jacobson in 1822(1) was not proved functional until 1948 by Sperber(2). In the bird the external iliac vein (EIV) communicates with the internal iliac vein which drains into the renal parenchyma. The EIV also connects directly to the renal vein (RV) by a large venous shunt. Interposed at the point of communication from EIV to RV is a valve-like structure described by Spanner (3) which is of variable shape in various species of birds but which is composed of smooth muscle, and usually has a conical shape with single or multiple apical openings. When contracted, the valve would tend to divert iliac vein blood through the kidney and when relaxed, blood would pass directly into the renal vein. Sperber described the position and appearance of the valve (Fig. 1) and presumed that it regulated blood flow to the renal tubules. Sperber clearly illustrated the functional significance of the renal portal system in the chicken by demonstrating that phenol red injected into one leg appeared in excess in the urine of the ipsilateral kidney. The present report deals with the response of this valve to autonomic drugs as determined by direct recording of the response of the isolated structure suspended in a smooth muscle bath, and as estimated by the excess excretion of para-aminohippurate by one kidney when this substance was injected into the ipsilateral leg or iliac vein. Method. In vitro. Valves were dissected from veins of freshly killed turkeys † weighing about 25 lb. The valve was suspended in oxygenated Tyrodes solution at 37.5° in an Anderson muscle bath and attached to a light weight lever recording on a smoked drum.

Renal tubular excretion of riboflavin in the chicken.

Summary Riboflavin excretion by renal tubular cells would seem to use the transport system for organic bases. This conclusion is based on the fact that tolazoline selectively inhibits riboflavin while not impairing PAH excretion. PAH excretion was even enhanced by tolazoline presumably as a result of diversion of more blood to the portal circulation. Benemid can inhibit transport of both PAH and riboflavin.

Effect of Renal Transplantation on the Levels of Choline in the Plasma of Uremic Humans

Plasma choline levels were measured in patients who received a kidney transplant, in donors who underwent nephrectomy and in nonrenal surgical patients. Choline was measured using a choline kinase assay. Choline levels in patients receiving a kidney fell from 29.8 +/- 1.86 microM before transplantation to 15.7 +/- 2.32 1 day later; this normal level was maintained for at least 7 months and in a single case for 2 years. Kidney donors and nonrenal surgery patients showed a significant decrease in plasma choline on the day following surgery but choline levels returned to normal by 3 days after surgery. Thus a transplanted functional kidney reduced the high plasma choline levels, associated with uremia, to normal and maintained these normal levels throughout the period of observation.