We studied the distribution of the extracellular matrix proteins fibronectin (FN) and laminin (LM) in the hypertrophied hearts of spontaneously hypertensive rats (SHR), using an immunofluorescence method with specific antibodies. The immunohistochemical reaction was positive in the cytoplasm of some hypertrophied cardiomyocytes. The results showed that FN and LM can be used as markers for tunnels, i.e. intracardiocytic invaginations of the sarcolemma. The tunnels observed contained capillaries.

The interferomemc technique has been used to measure the alkaline phosphatase activity in the kidney and small intestine. The effect of post-mortem autolysis on the activity of this enzyme was checked in specimens taken from five normal rabbits. The results were entirely reproducible. The limitations of the method are discussed and the possible sources of error analysed.

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