Jens Anker Larsen

The existence of tubulo-cisternal endoplasmic reticulum in rat hepatocytes

SummaryRat livers were fixed by perfusion with glutaraldehyde via the portal vein and postfixed with a mixture of osmium tetroxide and potassium ferricyanide. Subsurface cisterns and vesicles were demonstrated, and, from serial sections, it appears that these organelles are part of large, fenestrated cisterns situated parallel to and at a distance of 20–40 nm from the lateral plasma membrane. Some of the cisterns possessed ribosomes on the surface facing the interior of the cell and, at points, they were continuous with the endoplasmic reticulum. From the lateral cisterns, tubules approached the plasma membrane facing the space of Disse and the sinusoid. A network of tubules was found in the vicinity of the bile canaliculus; a part of it lay close to the canalicular plasma membrane. Serial sectioning revealed that this network was continuous with the lateral cisterns via the endoplasmic reticulum. This morphology resembles that of tubulo-cisternal endoplasmic reticulum of such transporting epithelia as the choroid plexus and the renal proximal tubules.

Vascular effects of vanadate.

SummaryThe present experiments demonstrate that vanadate (sodium orthovanadate) given i.v. to anesthetized cats induces a marked, transient and reversible constriction of visceral arteries, including the renal artery, whereas the femoral and carotid artery escape constriction. The constriction of the renal artery is accompanied by a pronounced reduction of glomerular filtration rate and urine production. The vasoconstriction appears to be caused by a direct effect of vanadate on the vessel wall, but the mechanism of action is not established.ZusammenfassungVanadat wurde als Na3VO4 anästhesierten Katzen i.v. gegeben.Ein deutlicher, kurzzeitiger und reversibler vasokonstriktorischer Effekt wurde registriert an den viszeralen Arterien (auch A. renalis), nicht aber an Femoralarterien und den Karotiden. Die Vasokonstriktion der Nierenarterien ist begleitet von einer hochgradigen Einschränkung der glomerulären Filtrationsrate und der Urinproduktion. Die gemessene Vasokonstriktion scheint die Folge einer direkten Vandatwirkung auf die Gefäßwand zu sein, deren Mechanismus nicht bekannt ist.