By Bruno Federowski SAO PAULO, April 28 (Reuters) - The Brazilian real weakened in volatile trading on Friday as traders assessed the implications of nationwide strikes led by Brazilian unions to protest President Michel Temer's austerity measures.

Some investors worried that the demonstrations could hamper Temer's campaign to raise lawmaker support for reforms of the country's pension system and labor laws, seen as key to lift Latin America's largest economy from a deep recession.

Others argued that uncertainty had already reflected on asset prices, after tight votes in Congress last week raised doubts over the government's strength.

The Brazilian real fell as much as 1 percent after strengthening 0.3 percent in early trading.

Volatility also spiked ahead of the settlement of the month-end Ptax rate, which is widely used to price foreign exchange contracts in Brazil.

The country's benchmark Bovespa stock index, however, was firmly up, reacting to a heavy batch of corporate updates.

Shares of GPA SA were the biggest gainers after stronger-than-expected margins helped Brazil's largest retailer swing to a profit in the first quarter.

Trading in other Latin American markets was muted, with traders mostly shrugging off weaker-than-expected U.S. gross domestic product figures. The Chilean peso fell 0.6 percent, while the Mexican peso rose 0.5 percent.

Key Latin American stock indexes and currencies at 1600 GMT: Stock indexes daily % YTD % change change Latest MSCI Emerging Markets 977.56 -0.21 13.61 MSCI LatAm 2601.92 0.24 10.89 Brazil Bovespa 65191.81 0.8 8.24 Mexico IPC 49329.30 -0.23 8.08 Chile IPSA 4800.70 0.37 15.64 Chile IGPA 24110.04 0.3 16.28 Argentina MerVal 20933.01 0.2 23.73 Colombia IGBC 10135.44 0.26 0.07 Venezuela IBC 56710.77 0.5 78.87 Currencies daily % YTD % change change Latest Brazil real 3.1896 -0.29 1.87 Mexico peso 18.9400 0.45 9.52 Chile peso 666.6 -0.59 0.62 Colombia peso 2947.55 -0.26 1.83 Peru sol 3.243 0.06 5.27 Argentina peso (interbank) 15.4250 0.11 2.92 Argentina peso (parallel) 15.91 0.25 5.72 (Reporting by Bruno Federowski; Editing by Dan Grebler)