Abstract--Additional well-crystallized kaolin from Washington County, Georgia, has been supplied to the Clay Minerals Society Source Clay Repository to replace the exhausted supply ofKGa-1. This kaolin is called KGa-1B and is from a geographic location and stratigraphic position close to where KGa-l was collected. Slight mineralogical and chemical differences are observed between KGa-1 and KGa-1B. KGa-1B crude appears slightly better crystalline than KGa-1, and it has a slightly higher titania content than KGa-1. The A1203, SIP2, Fe203, alkali, and alkaline earth contents appear similar for both samples. KGa-1 has a slightly coarser particle size than KGa-1 B crude. More intensive post-depositional alteration may have cleansed and crystallized the KGa-IB material to a slightly greater degree than the KGa-1 material.

A B S T R A C T The saluretic effect of the thiazide diuretics has been attributed to inhibition of sodium reabsorption in the distal nephron of the kidney. Recent micropuncture studies have shown, however, that chlorothiazide administration can also inhibit sodium reabsorption in the proximal convolution. To clarify the site of the saluretic effect of chlorothiazide, these micropuncture studies examined the effect of chlorothiazide on chloride transport in the nephron. The effect of chlorothiazide on chloride transport was studied because chlorothiazide's effectiveness as a saluretic is largely due to its ability to enhance sodium chloride excretion; if only changes in sodium transport are examined, it would be then difficult to determine if sodium as bicarbonate or as chloride is affected, since chlorothiazide can inhibit carbonic anhydrase. One group of rats was studied before and after 15 mg/kg per h chlorothiazide. For comparison, another group of rats was studied before and after 2 mg/kg per h benzolamide, a carbonic anhydrase inhibitor. Fractional chloride delivery from the proximal tubule was similarly increased in both groups; from 59.4 to 71.0% by chlorothiazide administration, P < 0.001, and from 54.3 to 68.2% by benzolamide administration, P < 0.001. The increased delivery of chloride from the proximal tubule was largely reabsorbed before the early distal tubule as fractional chloride delivery to this site increased only from 5.08 to 7.40% after chlorothiazide administration, P <0.001, and from 4.50 to 6.29% after benzolamide administration, P <0.01. Benzolamide had no effect on chloride reabsorption in the distal convoluted tubule. However, chlorothiazide administration resulted in a marked decrease in distal tubular chloride reabsorption, the fraction of filtered chloride present at the late distal tubule Portions of this paper appeared as abstracts in

A B S T R A C T The flow rate of tubular fluid has been suggested as one of several factors which may influence potassium transport in the distal convoluted tubule of the kidney. In the present micropuncture studies, the relationship between the flow rate of distal tubular fluid and potassium transport was examined in four groups of rats. Three groups of rats (I, II, and IV) were fed normal rat chow before study whereas one group (III) was fed chow containing 10% KC1. Group II received 10-20 pg/kg per h of d-aldosterone throughout the study.Distal tubular potassium transport in groups I, II, and III was examined before and after an increase in the flow rate of distal tubular fluid as induced by the infusion of an isotonic saline-bicarbonate solution equivalent to 10% of body weight. In group IV, distal tubular potassium transport was examined before and after enhancement of the flow rate by the infusion of hypertonic (15%) mannitol.In all four groups, distal tubular potassium secretion increased as the flow rate of tubular fluid increased. The nature of the relationship between distal tubular potassium transport and tubular fluid flow rate, however, was influenced by the extent to which the tubular fluid to plasma potassium ratio in the late distal tubule varied as the flow rate increased. As the flow rate was increased this ratio decreased significantly and to a comparable extent in groups I and II. In groups III and IV, on the other hand, this ratio was essentially identical during hydropenia and after the increase in the flow rate of tubular fluid. As a result, the increment in the amount of potassium present at the late distal tubule, which occurred as the flow rate increased, was significantly greater in groups III and IV than in groups I and II. The contrast in the relationship between the This work was presented in part at the American Society of Nephrology, Washington, D. C., November, 1973. Received for publication 10 May 1974 and in revised form 16 August 1974.flow rate of distal tubular fluid and potassium transport which were observed, probably reflects differences in the net driving force for cell to lumen potassium movement. Seemingly, the net driving force for potassium movement was maintained, as the flow rate of tubular fluid increased, by chronic potassium loading in group III and by hypertonic mannitol infusion in group IV.In groups I and II, the net driving force for potassium movement decreased as the flow rate of tubular fluid increased. However, the net driving force did not decrease in proportion to the increase in flow rate since potassium secretion was increased by increments in flow rate in these groups as well. We conclude that our results are consistent with the view that the flow rate of tubular fluid is a factor which can affect distal tubular potassium transport. However, the nature of the relationship between the flow rate of tubular fluid and potassium transport appears to depend upon the degree to which the driving force for cell to lumen potassium movement changes as the flo...