This Month in RES History - June '22

This Month in RES History

Join Communication Committee member Samson Kosemani as he looks back into the great science hidden in the RES archives.

The Uptake and Disposition of S35-Heparin by Macrophages In Vitro

According to histochemical investigations, macrophages can ingest both exogenous and endogenous heparin and retain it in the form of metachromatic granules similar to those found in mast cells. Furthermore, the metachromasia that occurs in macrophages after mast cell granule absorption decreases over time and eventually vanishes. According to earlier research, heparin increases the mobility and amount of pinocytic vesicles in peritoneal macrophages, implying that macrophages are involved in heparin sequestration and possibly breakdown. To test this hypothesis, Oh and colleagues used more sensitive methods than previously used to investigate the absorption of heparin by macrophages and its eventual destiny.

Oh and colleagues observed an initial slow uptake of incorporation of 35S-heparin by mouse peritoneal macrophages in vitro after three days, which was followed by a sharp increase in the rate of incorporation, indicating that peritoneal macrophages exhibit latency in their capacity for incorporating heparin. The second phase of uptake coincides with the period when a marked reduction in cell numbers occurs, as indicated by the decline in DNA.

This uptake was inhibited by unlabelled heparin, and unexpectedly, they also discovered the inhibitory effect of hyaluronic acid. To support their hypothesis, metachromasia appears in macrophages, but after 72 h,  the intensity of the reaction diminishes and finally disappears. Oh and colleagues concluded that heparin, once incorporated by macrophages is retained for relatively long periods without degradation.


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