Bodily Secretions/chemistry; Insulin-Secreting Cells/drug effects; Insulin/metabolism; Peptides/analysis; Peptides/pharmacology; Rana catesbeiana/metabolism; Skin/metabolism; Amino Acid Sequence; Amphibian Proteins/analysis; Amphibian Proteins/chemistry; Amphibian Proteins/isolation & purification; Amphibian Proteins/pharmacology; Animals; Antimicrobial Cationic Peptides/analysis; Antimicrobial Cationic Peptides/chemistry; Antimicrobial Cationic Peptides/isolation & purification; Antimicrobial Cationic Peptides/pharmacology; Cell Line; Cell Survival/drug effects; Chromatography, High Pressure Liquid; Insulin Secretion; Insulin-Secreting Cells/metabolism; Molecular Sequence Data; Molecular Weight; Peptides/chemistry; Peptides/isolation & purification; Protein Isoforms/analysis; Protein Isoforms/chemistry; Protein Isoforms/isolation & purification; Protein Isoforms/pharmacology; Proteins/analysis; Proteins/chemistry; Proteins/isolation & purification; Proteins/pharmacology; Rats; Spectrometry, Mass, Electrospray Ionization