The investigation described was done to study the relation of Na+offering to the glucose-and PAl-I-transport. Therefore isolated kidneys of Rana ridibunda were perfused with solutions of NaC1 and Na~SO 4 at various concentrations either from the blood-and lumenside or only from one of both. After perfusion under various conditions, the extracellnlar volume and the Na+-concentration of the kidney tissue per gram of fresh weight were measured.
The transport of glucose (reabsorption) is dependent on Na + in the following ways : The more Na + is transported the more glucose is transported and vice versa. The proportion of transported Na+/transported glucose is shifted ifl favour of the latter when the supply of sodium is at a low level. Only Na + on the lumenside is essential for the transport of glucose. The Na+-transport is lower when it is given as SOt--than as C1-. This is explained by the relative impermeability of the tubule cell for the SOt---anion. In this ease--low Na+-transport--the reabsorption of glucose comes up to the same rate which is measured when NaC1 is given. These results indicate that the Na+-transport is not the decisive parameter for the interdepence of Na + and transport of other substances.
A similar situation is given in the experiments with PAH: More PAH is transported (secretion) when much Na + is offered and vice versa. With a low supply of Na + the proportion of transported Na+/transported PAH was also shifted in favour of PAH. The best PAH-transport was observed when Na + was given from the lumenand the bloodside. Na +, offered only from the bloodside, decreases the transport of PAH but not as much as it was seen for the decrease of the glucose-transport. This is a rnle for all PAI-I-eoneentrations below or above the saturation limit of the Tin. The results were the same for NaC1 and for Na~SO~.
The Na+-contents of the kidneys were diminished not very much when Na + was supplied only from the himenside, but a very strong diminution was seen when it was supplied only from the bloodside. The kidneys probably lose intrace]lular Na+ under these conditions.
The described experiments and other ones in which the Na+-transport was diminished by cardiotonie steroids and Fursemide lead to the following conclusion: The intraeellnlar concentration as well as the transport of Na + are connected with the transcellular transport of glucose and PAH. The possible mechanism for the role played by Na + is discussed.
Zusammen/assung. Zur Abk]~rung der Frage, fiber welehen Parameter: intra-cellnl~re, extracellnli~re Konzentration oder Transport Na + mit dem Glucose-oder PAH-Transport verknfipft ist, wurde isolierten Nieren yon Rana ridibunda LSsungen verschiedener NaC1-und Na2SO4-Konzentration auf der Lumen-und der Blutseite oder auf der Lumen-resp. der Blutseite angeboten. Nach Perfusion unter