Table 1.

Compositions of solutions (mM)

	KCl	NaCl	NaMeSO3	CaCl2	CaGluc	MgCl2	MgGluc	HEPES	BAPTA	Dibromo-BAPTA	d-Glucose
Cytoplasmic
0.1–0.3 μM Free Ca2+	140	5		0.7–1.2		2		5	2		5
3 μM Free Ca2+	140	5		1.4		2		5		2	5
Unbuffered Ca2+	140	5		0.03–10		2		5			5
High-Na+ (Ca2+unbuffered)		145		1		2		5			5
High-K+ (Ca2+unbuffered)	145			0.1–1		2		5			5
Cl−-free (Ca2+unbuffered)			145		1		2	5			5

	NaCl	KCl	CaCl2	MgCl2	HEPES	NaPyr	d-Glucose
External
Standard	140	5	2	2	5	2	9.4
High-K+		145	2	2	5	2	9.4
High-Ca2+			100	2	5		9.4

For each reagent, total concentrations are shown. NaMeSO₃, sodium methanesulfonate; CaGluc, calcium gluconate; MgGluc, magnesium gluconate; NaPyr, sodium pyruvate. Total and free Ca²⁺ were the same in the unbuffered high-Ca²⁺ solutions. BAPTA and dibromo-BAPTA were added as the tetrapotassium salts. Solutions were adjusted to pH 7.4 with NaOH (high-Na⁺ solutions), KOH (high-K⁺ solutions), or Tris base (high-Ca²⁺ external solution).