The Neonatal Cardiomyocyte Isolation System has been introduced to provide researchers with a reliable, convenient, and consistent cell isolation system. By utilizing purified rather than crude enzyme preparations, it has been possible to minimize the lot-to-lot variation. In addition, United States Biological use-tests the kits by isolating cardiomyocytes from neonatal rat hearts to assure performance, reliability and consistent yield of viable cells. The kit has been formulated in conjunction with Dr. Ronal MacGregor. The method is based on that described by Toraason, et al. (1988) in which the minced tissue is incubated overnight with purified trypsin at 4°C. As pointed out by Toraason, this step reduces the hands-on time required to harvest cells compared to the time involved in sequential incubations in warm trypsin or collagenase. Also, purified collagenase is utilized to maximize yield and viability. This kit contains sufficient materials for five separate tissue dissociations, each containing up to twelve hearts. For larger or smaller tissue samples prepare proportionate volumes ofreagents at each step and combine them in the same ratio as described in the protocol.Kit Components:N1057-01: Hank's Buffer, 1x500ml Sterile calcium- and magnesium-free Hank's Balanced Salt Solution, pH 7.4. The solution is used for reconstituting N1057-02 Trypsin and N1057-03 Inhibitor in addition to serving as the medium for the dissociation.N1057-02: Trypsin Vials, 5x1000ug, 3X crystallized, dialyzed against 1mM HCl, filtered through 0.22um pore size membrane, and lyophilized. Reconstitute with 2ml N1057-01 Hank's Buffer and swirl gently to dissolve contents. Store at 4°C.N1057-03: Inhibitor Vials, 5x2000ug Supplied as a 0.22um membrane filtered, lyophilized powder. Reconstitute with 1ml N1057-01 Hank's Buffer and swirl gently to dissolve contents. Store at 4°C.N1057-04: Collagenase Vials 5x1500 Units Supplied as a 0.22um membrane filtered, lyophilized powder which has been chromatographically purified. It contains <50 caseinase units/mg and is composed of two separable but very similar collagenases. Reconstitute with 5ml prepared N1057-05 L-15 Media Powder and swirl gently to dissolve contents. Store at 4°C.N1057-05: L-15 Media Powder, 1x1L Reconstitute entire contents of pouch by cutting open top of envelope and pouring contents into beaker containing 800ml of cell culture grade water. Rinse pouch 2-3 times with additional 100ml. Bring total volume to 1 liter and filter through a 0.22um filter.N1057-06: Cell Strainers (Falcon), 5 and a card correlating phenol red color with pH for checking the pH of balanced salt solution and culture medium.Storage and Stability:May be stored at 4°C. Stable for 6 months.