TABLE 4.

ED₅₀s (concentrations giving 50% Ca²⁺ release and TPP⁺ uptake) of polyamines with appropriate hydrophobic groups^a

Cationic substance	Concn giving:
	Ca2+ release (μM)	TPP+ uptake (μM)
PMBN	5-10	10-20
Benzylamine	>500	>500
N-Benzylethylenediamine	200-500	>500
4-N-Benzylspermidine	20-50	500
1-Naphthylacetylspermine	5-10	5-10
Methoctramine	—b	20-50

^aAmounts of Ca²⁺ release and TPP⁺ uptake induced by the incubation of cells with 100 μM PMBN for 3 min were defined as 100% as in Table 3.

^bCa²⁺ release could not be measured owing to interference with the electrode.