Development of storage granules during megakaryocyte maturation: accumulation of adenine nucleotides and the capacity for serotonin sequestration

Abstract

The specific release of platelet-dense body constituents such as adenine nucleotides and serotonin has a fundamental role in hemostasis. The content of adenine nucleotides in platelet dense bodies is probably established in megakaryocytes, but very little is known about this process. To gain a better understanding of platelet development, we studied the storage and metabolic pools of adenine nucleotides and the capacity for serotonin sequestration in storage granules during megakaryocyte maturation. Megakaryocytes were isolated from guinea pig bone marrow and separated in subgroups at different phases of maturation. The sequestration of adenine nucleotides and serotonin in storage granules was assessed by using calcium ionophore to induce secretion under nonlytic conditions, and metabolic pool adenine nucleotides were evaluated by using digitonin under controlled lysis conditions. The study showed that there were similar amounts of cytoplasmic adenosine triphosphate (ATP) in the mature and immature fractions based on digitonin-induced controlled lysis (1.26 +/- 0.37 nmol/microgram phosphorus vs 1.23 +/- 0.44 nmol/microgram phosphorus). However, only the mature cells contained a significant amount of storage pool ATP (0.41 +/- 0.19 nmol/microgram phosphorus vs 0.05 +/- 0.05 nmol/microgram phosphorus) released in response to A23187. The subgroups of megakaryocytes contained equal amounts of total adenosine diphosphate (ADP) extractable with ethanol (0.49 +/- 0.14 nmol/microgram phosphorus vs 0.55 +/- 0.50 nmol/microgram phosphorus) but only mature cells contained ADP in the storage granules (0.25 +/- 0.13 nmol/microgram phosphorus vs 0.07 +/- 0.05 nmol/microgram phosphorus).(ABSTRACT TRUNCATED AT 250 WORDS)