Macula densa morphology in diabetic rats with and without hyperglycemia and in nondiabetic hyperglycemic rats.
The morphology of the macula densa was studied in streptozotocin diabetic insulin-treated rats with hyperglycemia for 50 days, and in three groups of diabetic rats that were first hyperglycemic for 50 days and then put onto different insulin regimes to achieve normoglycemia. One of the latter groups of rats was given a single dose of insulin and was studied 4 hours later when the animals were normoglycemic. The other two groups were treated with insulin for 5 and 15 days in such a way that the animals were nearly normoglycemic throughout the treatment period. In a further set of experiments two groups of nondiabetic rats were made hyperglycemic by intravenous injection of glucose and studied after 1 and 10 minutes of hyperglycemia. A perfusion fixation of the kidneys was performed in all animals with a 1% glutaraldehyde solution retrograde through the aorta, and the tissue was embedded in Epon for light and electron microscopy. Juxtaglomerular apparatuses were randomly selected from thick sections and reembedded for electron microscopy. The volume density of the lateral intercellular spaces (LIS) between the macula densa cells was determined on electron micrographs, by use of a morphometric technique. The study showed that the volume density of the LIS comprised about 10% in the nondiabetic normoglycemic animals and about 1.5% in the diabetic hyperglycemic animals. In all the insulin-treated normoglycemic diabetic animals, the volume density of the LIS was the same as in the nondiabetic normoglycemic animals (about 10%), independent of the duration of the insulin treatment. In the nondiabetic hyperglycemic animals the volume density of the LIS comprised about 1.5%, as in the diabetic hyperglycemic animals. In conclusion, the volume density of the LIS between the macula densa cells is reduced in a hyperglycemic state, irrespective of how the hyperglycemia was achieved, and they are normalized (i.e., enlarged) in insulin-treated diabetic normoglycemic animals irrespective of the duration of the treatment. The results indicate that changes in the blood glucose concentration have a major impact on the size of the macula densa LIS.
Rasch
R
R
Department of Cell Biology, University of Aarhus, Denmark.
Holck
P
P
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000473:pathology*; D005260:Female; D006943:Hyperglycemia / Q000097:blood / Q000150:complications / Q000473:pathology*; D007328:Insulin / Q000494:pharmacology; D007668:Kidney / Q000473:pathology; D008854:Microscopy, Electron; D009399:Nephrons / Q000473:pathology* / Q000648:ultrastructure; D009929:Organ Size; D051381:Rats; D011919:Rats, Inbred Strains
D001786:Blood Glucose; D007328:Insulin